Artículos de revistas: "CDC50 proteins"

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Furuta, Nobumichi, Konomi Fujimura-Kamada, Koji Saito, Takaharu Yamamoto y Kazuma Tanaka. "Endocytic Recycling in Yeast Is Regulated by Putative Phospholipid Translocases and the Ypt31p/32p–Rcy1p Pathway". Molecular Biology of the Cell 18, n.º 1 (enero de 2007): 295–312. http://dx.doi.org/10.1091/mbc.e06-05-0461.

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Phospholipid translocases (PLTs) have been implicated in the generation of phospholipid asymmetry in membrane bilayers. In budding yeast, putative PLTs are encoded by the DRS2 gene family of type 4 P-type ATPases. The homologous proteins Cdc50p, Lem3p, and Crf1p are potential noncatalytic subunits of Drs2p, Dnf1p and Dnf2p, and Dnf3p, respectively; these putative heteromeric PLTs share an essential function for cell growth. We constructed temperature-sensitive mutants of CDC50 in the lem3Δ crf1Δ background (cdc50-ts mutants). Screening for multicopy suppressors of cdc50-ts identified YPT31/32, two genes that encode Rab family small GTPases that are involved in both the exocytic and endocytic recycling pathways. The cdc50-ts mutants did not exhibit major defects in the exocytic pathways, but they did exhibit those in endocytic recycling; large membranous structures containing the vesicle-soluble N-ethylmaleimide-sensitive factor attachment protein receptor Snc1p intracellularly accumulated in these mutants. Genetic results suggested that the YPT31/32 effector RCY1 and CDC50 function in the same signaling pathway, and simultaneous overexpression of CDC50, DRS2, and GFP-SNC1 restored growth as well as the plasma membrane localization of GFP-Snc1p in the rcy1Δ mutant. In addition, Rcy1p coimmunoprecipitated with Cdc50p-Drs2p. We propose that the Ypt31p/32p–Rcy1p pathway regulates putative phospholipid translocases to promote formation of vesicles destined for the trans-Golgi network from early endosomes.

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Saito, Koji, Konomi Fujimura-Kamada, Nobumichi Furuta, Utako Kato, Masato Umeda y Kazuma Tanaka. "Cdc50p, a Protein Required for Polarized Growth, Associates with the Drs2p P-Type ATPase Implicated in Phospholipid Translocation in Saccharomyces cerevisiae". Molecular Biology of the Cell 15, n.º 7 (julio de 2004): 3418–32. http://dx.doi.org/10.1091/mbc.e03-11-0829.

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Cdc50p, a transmembrane protein localized to the late endosome, is required for polarized cell growth in yeast. Genetic studies suggest that CDC50 performs a function similar to DRS2, which encodes a P-type ATPase of the aminophospholipid translocase (APT) subfamily. At low temperatures, drs2Δ mutant cells exhibited depolarization of cortical actin patches and mislocalization of polarity regulators, such as Bni1p and Gic1p, in a manner similar to the cdc50Δ mutant. Both Cdc50p and Drs2p were localized to the trans-Golgi network and late endosome. Cdc50p was coimmunoprecipitated with Drs2p from membrane protein extracts. In cdc50Δ mutant cells, Drs2p resided on the endoplasmic reticulum (ER), whereas Cdc50p was found on the ER membrane in drs2Δ cells, suggesting that the association on the ER membrane is required for transport of the Cdc50p-Drs2p complex to the trans-Golgi network. Lem3/Ros3p, a homolog of Cdc50p, was coimmunoprecipitated with another APT, Dnf1p; Lem3p was required for exit of Dnf1p out of the ER. Both Cdc50p-Drs2p and Lem3p-Dnf1p were confined to the plasma membrane upon blockade of endocytosis, suggesting that these proteins cycle between the exocytic and endocytic pathways, likely performing redundant functions. Thus, phospholipid asymmetry plays an important role in the establishment of cell polarity; the Cdc50p/Lem3p family likely constitute potential subunits specific to unique P-type ATPases of the APT subfamily.

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García-Sánchez, Sebastián, María P. Sánchez-Cañete, Francisco Gamarro y Santiago Castanys. "Functional role of evolutionarily highly conserved residues, N-glycosylation level and domains of the Leishmania miltefosine transporter-Cdc50 subunit". Biochemical Journal 459, n.º 1 (14 de marzo de 2014): 83–94. http://dx.doi.org/10.1042/bj20131318.

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Cdc50 proteins are associated with phospholipid translocating P4-ATPases. Highly conserved and N-glycosylated residues of LiRos3, a Leishmania infantum Cdc50 protein, play a role in correct trafficking to the plasma membrane and in the activity of the miltefosine transporter.

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López-Marqués, Rosa L., Lisbeth R. Poulsen, Susanne Hanisch, Katharina Meffert, Morten J. Buch-Pedersen, Mia K. Jakobsen, Thomas Günther Pomorski y Michael G. Palmgren. "Intracellular Targeting Signals and Lipid Specificity Determinants of the ALA/ALIS P4-ATPase Complex Reside in the Catalytic ALA α-Subunit". Molecular Biology of the Cell 21, n.º 5 (marzo de 2010): 791–801. http://dx.doi.org/10.1091/mbc.e09-08-0656.

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Members of the P4 subfamily of P-type ATPases are believed to catalyze flipping of phospholipids across cellular membranes, in this way contributing to vesicle biogenesis in the secretory and endocytic pathways. P4-ATPases form heteromeric complexes with Cdc50-like proteins, and it has been suggested that these act as β-subunits in the P4-ATPase transport machinery. In this work, we investigated the role of Cdc50-like β-subunits of P4-ATPases for targeting and function of P4-ATPase catalytic α-subunits. We show that the Arabidopsis P4-ATPases ALA2 and ALA3 gain functionality when coexpressed with any of three different ALIS Cdc50-like β-subunits. However, the final cellular destination of P4-ATPases as well as their lipid substrate specificity are independent of the nature of the ALIS β-subunit they were allowed to interact with.

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Hanadate, Yuki, Yumiko Saito-Nakano, Kumiko Nakada-Tsukui y Tomoyoshi Nozaki. "Identification and Characterization of the Entamoeba Histolytica Rab8a Binding Protein: A Cdc50 Homolog". International Journal of Molecular Sciences 19, n.º 12 (30 de noviembre de 2018): 3831. http://dx.doi.org/10.3390/ijms19123831.

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Membrane traffic plays a pivotal role in virulence in the enteric protozoan parasite Entamoeba histolytica. EhRab8A small GTPase is a key regulator of membrane traffic at the endoplasmic reticulum (ER) of this protist and is involved in the transport of plasma membrane proteins. Here we identified the binding proteins of EhRab8A. The Cdc50 homolog, a non-catalytic subunit of lipid flippase, was identified as an EhRab8A binding protein candidate by affinity coimmunoprecipitation. Binding of EhRab8A to EhCdc50 was also confirmed by reciprocal immunoprecipitation and blue-native polyacrylamide gel electrophoresis, the latter of which revealed an 87 kDa complex. Indirect immunofluorescence imaging with and without Triton X100 showed that endogenous EhCdc50 localized on the surface in the absence of permeabilizing agent but was observed on the intracellular structures and overlapped with the ER marker Bip when Triton X100 was used. Overexpression of N-terminal HA-tagged EhCdc50 impaired its translocation to the plasma membrane and caused its accumulation in the ER. As reported previously in other organisms, overexpression and accumulation of Cdc50 in the ER likely inhibited surface transport and function of the plasma membrane lipid flippase P4-ATPase. Interestingly, HA-EhCdc50-expressing trophozoites gained resistance to miltefosine, which is consistent with the prediction that HA-EhCdc50 overexpression caused its accumulation in the ER and mislocalization of the unidentified lipid flippase. Similarly, EhRab8A gene silenced trophozoites showed increased resistance to miltefosine, supporting EhRab8A-dependent transport of EhCdc50. This study demonstrated for the first time that EhRab8A mediates the transport of EhCdc50 and lipid flippase P4-ATPase from the ER to the plasma membrane.

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Bryde, Susanne, Hanka Hennrich, Patricia M. Verhulst, Philippe F. Devaux, Guillaume Lenoir y Joost C. M. Holthuis. "CDC50 Proteins Are Critical Components of the Human Class-1 P4-ATPase Transport Machinery". Journal of Biological Chemistry 285, n.º 52 (20 de octubre de 2010): 40562–72. http://dx.doi.org/10.1074/jbc.m110.139543.

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7

van der Velden, Lieke M., Catharina G. K. Wichers, Adriana E. D. van Breevoort, Jonathan A. Coleman, Robert S. Molday, Ruud Berger, Leo W. J. Klomp y Stan F. J. van de Graaf. "Heteromeric Interactions Required for Abundance and Subcellular Localization of Human CDC50 Proteins and Class 1 P4-ATPases". Journal of Biological Chemistry 285, n.º 51 (14 de octubre de 2010): 40088–96. http://dx.doi.org/10.1074/jbc.m110.139006.

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Misu, Kenjiro, Konomi Fujimura-Kamada, Takashi Ueda, Akihiko Nakano, Hiroyuki Katoh y Kazuma Tanaka. "Cdc50p, a Conserved Endosomal Membrane Protein, Controls Polarized Growth in Saccharomyces cerevisiae". Molecular Biology of the Cell 14, n.º 2 (febrero de 2003): 730–47. http://dx.doi.org/10.1091/mbc.e02-06-0314.

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During the cell cycle of the yeast Saccharomyces cerevisiae, the actin cytoskeleton and the growth of cell surface are polarized, mediating bud emergence, bud growth, and cytokinesis. We identified CDC50 as a multicopy suppressor of the myo3 myo5-360 temperature-sensitive mutant, which is defective in organization of cortical actin patches. The cdc50 null mutant showed cold-sensitive cell cycle arrest with a small bud as reported previously. Cortical actin patches and Myo5p, which are normally localized to polarization sites, were depolarized in the cdc50 mutant. Furthermore, actin cables disappeared, and Bni1p and Gic1p, effectors of the Cdc42p small GTPase, were mislocalized in the cdc50 mutant. As predicted by its amino acid sequence, Cdc50p appears to be a transmembrane protein because it was solubilized from the membranes by detergent treatment. Cdc50p colocalized with Vps21p in endosomal compartments and was also localized to the class E compartment in thevps27 mutant. The cdc50 mutant showed defects in a late stage of endocytosis but not in the internalization step. It showed, however, only modest defects in vacuolar protein sorting. Our results indicate that Cdc50p is a novel endosomal protein that regulates polarized cell growth.

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Li, Xin, Baohui Chen, Sawako Yoshina, Tanxi Cai, Fuquan Yang, Shohei Mitani y Xiaochen Wang. "Inactivation of Caenorhabditis elegans aminopeptidase DNPP-1 restores endocytic sorting and recycling in tat-1 mutants". Molecular Biology of the Cell 24, n.º 8 (15 de abril de 2013): 1163–75. http://dx.doi.org/10.1091/mbc.e12-10-0730.

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In Caenorhabditis elegans, the P4-ATPase TAT-1 and its chaperone, the Cdc50 family protein CHAT-1, maintain membrane phosphatidylserine (PS) asymmetry, which is required for membrane tubulation during endocytic sorting and recycling. Loss of tat-1 and chat-1 disrupts endocytic sorting, leading to defects in both cargo recycling and degradation. In this study, we identified the C. elegans aspartyl aminopeptidase DNPP-1, loss of which suppresses the sorting and recycling defects in tat-1 mutants without reversing the PS asymmetry defect. We found that tubular membrane structures containing recycling cargoes were restored in dnpp-1 tat-1 double mutants and that these tubules overlap with RME-1–positive recycling endosomes. The restoration of the tubular structures in dnpp-1 tat-1 mutants requires normal functions of RAB-5, RAB-10, and RME-1. In tat-1 mutants, we observed alterations in membrane surface charge and targeting of positively charged proteins that were reversed by loss of dnpp-1. DNPP-1 displays a specific aspartyl aminopeptidase activity in vitro, and its enzymatic activity is required for its function in vivo. Our data reveal the involvement of an aminopeptidase in regulating endocytic sorting and recycling and suggest possible roles of peptide signaling and/or protein metabolism in these processes.

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Park, Chong J., Sukgil Song, Thomas H. Giddings, Hyeon-Su Ro, Krisada Sakchaisri, Jung-Eun Park, Yeon-Sun Seong, Mark Winey y Kyung S. Lee. "Requirement for Bbp1p in the Proper Mitotic Functions of Cdc5p in Saccharomyces cerevisiae". Molecular Biology of the Cell 15, n.º 4 (abril de 2004): 1711–23. http://dx.doi.org/10.1091/mbc.e03-07-0461.

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The polo-box domain of the budding yeast polo kinase Cdc5p plays an essential role for targeting the catalytic activity of Cdc5p to spindle pole bodies (SPBs) and cytokinetic neck-filaments. Here, we report the isolation of Bbp1p as a polo-box interacting protein by a yeast two-hybrid screen. Bbp1p localizes to the periphery of the central plaque of the SPB and plays an important role in SPB duplication. Similarly, Cdc5p localized to the cytoplasmic periphery of the SPB. In vitro binding studies showed that Cdc5p interacted with the N-terminal domain of Bbp1p (Bbp1pΔC), but apparently not with Mps2p, a component shown to form a stable complex with Bbp1p. In addition, Bbp1p, but likely not Mps2p, was required for proper localization of Cdc5p to the SPB. The C-terminal coiled-coil domain of Bbp1p (Bbp1p243–385), which is crucial for both the homodimerization and the SPB localization, could target the localization-defective Cdc5pΔC to the SPB and induce the release of Cdc14p from the nucleolus. Consistent with this observation, expression of CDC5ΔC-BBP1243–385 under CDC5 promoter control partially complemented the cdc5Δ defect. These data suggest that Bbp1pΔC interacts with the polo-box domain of Cdc5p, and this interaction is critical for the subcellular localization and mitotic functions of Cdc5p.

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Kabra, Ritika, Prajakta Ingale y Shailza Singh. "Computationally designed synthetic peptides for transporter proteins imparts allostericity in Miltefosine resistant L. major". Biochemical Journal 477, n.º 10 (29 de mayo de 2020): 2007–26. http://dx.doi.org/10.1042/bcj20200176.

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The emergence of drug resistance is a major concern for combating against Cutaneous Leishmaniasis, a neglected tropical disease affecting 98 countries including India. Miltefosine is the only oral drug available for the disease and Miltefosine transporter proteins play a pivotal role in the emergence of drug-resistant Leishmania major. The cause of resistance is less accumulation of drug inside the parasite either by less uptake of the drug due to a decrease in the activity of P4ATPase–CDC50 complex or by increased efflux of the drug by P-glycoprotein (P-gp, an ABC transporter). In this paper, we are trying to allosterically modulate the behavior of resistant parasite (L. major) towards its sensitivity for the existing drug (Miltefosine, a phosphatidylcholine analog). We have used computational approaches to deal with the conservedness of the proteins and apparently its three-dimensional structure prediction through ab initio modeling. Long scale membrane-embedded molecular dynamics simulations were carried out to study the structural interaction and stability. Parasite-specific motifs of these proteins were identified based on the machine learning technique, against which a peptide library was designed. The protein–peptide docking shows good binding energy of peptides Pg5F, Pg8F and PC2 with specific binding to the motifs. These peptides were tested both in vitro and in vivo, where Pg5F in combination with PC2 showed 50–60% inhibition in resistant L. major's promastigote and amastigote forms and 80–90% decrease in parasite load in mice. We posit a model system wherein the data provide sufficient impetus for being novel therapeutics in order to counteract the drug resistance phenotype in Leishmania parasites.

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Nakano, Kenzi, Takaharu Yamamoto, Takuma Kishimoto, Takehiro Noji y Kazuma Tanaka. "Protein Kinases Fpk1p and Fpk2p are Novel Regulators of Phospholipid Asymmetry". Molecular Biology of the Cell 19, n.º 4 (abril de 2008): 1783–97. http://dx.doi.org/10.1091/mbc.e07-07-0646.

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Type 4 P-type ATPases (flippases) are implicated in the generation of phospholipid asymmetry in membranes by the inward translocation of phospholipids. In budding yeast, the DRS2/DNF family members Lem3p-Dnf1p/Dnf2p and Cdc50p-Drs2p are putative flippases that are localized, respectively, to the plasma membrane and endosomal/trans-Golgi network (TGN) compartments. Herein, we identified a protein kinase gene, FPK1, as a mutation that exhibited synthetic lethality with the cdc50Δ mutation. The kinase domain of Fpk1p exhibits high homology to plant phototropins and the fungus Neurospora crassa NRC-2, both of which have membrane-associated functions. Simultaneous disruption of FPK1 and its homolog FPK2 phenocopied the lem3Δ/dnf1Δ dnf2Δ mutants, exhibiting the impaired NBD-labeled phospholipid uptake, defects in the early endosome-to-TGN pathway in the absence of CDC50, and hyperpolarized bud growth after exposure of phosphatidylethanolamine at the bud tip. The fpk1Δ fpk2Δ mutation did not affect the subcellular localization of Lem3p-Dnf1p or Lem3p-Dnf2p. Further, the purified glutathione S-transferase (GST)-fused kinase domain of Fpk1p phosphorylated immunoprecipitated Dnf1p and Dnf2p to a greater extent than Drs2p. We propose that Fpk1p/Fpk2p are upstream activating protein kinases for Lem3p-Dnf1p/Dnf2p.

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Ohi, Melanie D., Andrew J. Link, Liping Ren, Jennifer L. Jennings, W. Hayes McDonald y Kathleen L. Gould. "Proteomics Analysis Reveals Stable Multiprotein Complexes in Both Fission and Budding Yeasts Containing Myb-Related Cdc5p/Cef1p, Novel Pre-mRNA Splicing Factors, and snRNAs". Molecular and Cellular Biology 22, n.º 7 (1 de abril de 2002): 2011–24. http://dx.doi.org/10.1128/mcb.22.7.2011-2024.2002.

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ABSTRACT Schizosaccharomyces pombe Cdc5p and its Saccharomyces cerevisiae ortholog, Cef1p, are essential Myb-related proteins implicated in pre-mRNA splicing and contained within large multiprotein complexes. Here we describe the tandem affinity purification (TAP) of Cdc5p- and Cef1p-associated complexes. Using transmission electron microscopy, we show that the purified Cdc5p complex is a discrete structure. The components of the S. pombe Cdc5p/S. cerevisiae Cef1p complexes (termed Cwfs or Cwcs, respectively) were identified using direct analysis of large protein complex (DALPC) mass spectrometry (A. J. Link et al., Nat. Biotechnol. 17:676-682, 1999). At least 26 proteins were detected in the Cdc5p/Cef1p complexes. Comparison of the polypeptides identified by S. pombe Cdc5p purification with those identified by S. cerevisiae Cef1p purification indicates that these two yeast complexes are nearly identical in composition. The majority of S. pombe Cwf proteins and S. cerevisiae Cwc proteins are known pre-mRNA splicing factors including core Sm and U2 and U5 snRNP components. In addition, the complex contains the U2, U5, and U6 snRNAs. Previously uncharacterized proteins were also identified, and we provide evidence that several of these novel factors are involved in pre-mRNA splicing. Our data represent the first comprehensive analysis of CDC5-associated proteins in yeasts, describe a discrete highly conserved complex containing novel pre-mRNA splicing factors, and demonstrate the power of DALPC for identification of components in multiprotein complexes.

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McDonald, W. Hayes, Ryoma Ohi, Natalia Smelkova, David Frendewey y Kathleen L. Gould. "Myb-Related Fission Yeast cdc5p Is a Component of a 40S snRNP-Containing Complex and Is Essential for Pre-mRNA Splicing". Molecular and Cellular Biology 19, n.º 8 (1 de agosto de 1999): 5352–62. http://dx.doi.org/10.1128/mcb.19.8.5352.

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ABSTRACT Myb-related cdc5p is required for G2/M progression in the yeast Schizosaccharomyces pombe. We report here that all detectable cdc5p is stably associated with a multiprotein 40S complex. Immunoaffinity purification has allowed the identification of 10 cwf (complexed with cdc5p) proteins. Two (cwf6p and cwf10p) are members of the U5 snRNP; one (cwf9p) is a core snRNP protein. cwf8p is the apparent ortholog of the Saccharomyces cerevisiaesplicing factor Prp19p. cwf1 + is allelic to theprp5 + gene defined by the S. pombesplicing mutant, prp5-1, and there is a strong negative genetic interaction between cdc5-120 andprp5-1. Five cwfs have not been recognized previously as important for either pre-mRNA splicing or cell cycle control. Further characterization of cwf1p, cwf2p, cwf3p, and cwf4p demonstrates that they are encoded by essential genes, cosediment with cdc5p at 40S, and coimmunoprecipitate with cdc5p. We further show that cdc5p associates with the U2, U5, and U6 snRNAs and that cells lackingcdc5 + function are defective in pre-mRNA splicing. These data raise the possibility that the cdc5p complex is an intermediate in the assembly or disassembly of an active S. pombe spliceosome.

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Boronat, Susanna y Judith L. Campbell. "Mitotic Cdc6 Stabilizes Anaphase-Promoting Complex Substrates by a Partially Cdc28-Independent Mechanism, and This Stabilization Is Suppressed by Deletion of Cdc55". Molecular and Cellular Biology 27, n.º 3 (27 de noviembre de 2006): 1158–71. http://dx.doi.org/10.1128/mcb.01745-05.

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ABSTRACT Ectopic expression of Cdc6p results in mitotic delay, and this has been attributed to Cdc6p-mediated inhibition of Cdc28 protein kinase and failure to activate the anaphase-promoting complex (APC). Here we show that endogenous Cdc6p delays a specific subset of mitotic events and that Cdc28 inhibition is not sufficient to account for it. The depletion of Cdc6p in G2/M cells reveals that Cdc6p is rate limiting for the degradation of the APC/Cdc20 substrates Pds1p and Clb2p. Conversely, the premature expression of Cdc6p delays the degradation of APC/Cdc20 substrates. Abolishing Cdc6p/Cdc28p interaction does not eliminate the Cdc6-dependent delay of these anaphase events. To identify additional Cdc6-mediated, APC-inhibitory mechanisms, we looked for mutants that reversed the mitotic delay. The deletion of SWE1, RAD24, MAD2, or BUB2 had no effect. However, disrupting CDC55, a PP2A regulatory subunit, suppressed the Cdc6p-dependent delay of Pds1 and Clb2 destruction. A specific role for CDC55 was supported by demonstrating that the lethality of Cdc6 ectopic expression in a cdc16-264 mutant is suppressed by the deletion of CDC55, that endogenous Cdc6p coimmunoprecipitates with the Cdc55 and Tpd3 subunits of PP2A, that Cdc6p/Cdc55p/Tpd3 interaction occurs only during mitosis, and that Cdc6 affects PP2A-Cdc55 activity during anaphase. This demonstrates that the levels and timing of accumulation of Cdc6p in mitosis are appropriate for mediating the modulation of APC/Cdc20.

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Mui, Melissa Z., Diana E. Roopchand, Matthew S. Gentry, Richard L. Hallberg, Jackie Vogel y Philip E. Branton. "Adenovirus Protein E4orf4 Induces Premature APCCdc20 Activation in Saccharomyces cerevisiae by a Protein Phosphatase 2A-Dependent Mechanism". Journal of Virology 84, n.º 9 (17 de febrero de 2010): 4798–809. http://dx.doi.org/10.1128/jvi.02434-09.

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ABSTRACT Protein phosphatase 2A (PP2A) has been implicated in cell cycle progression and mitosis; however, the complexity of PP2A regulation via multiple B subunits makes its functional characterization a significant challenge. The human adenovirus protein E4orf4 has been found to induce both high Cdk1 activity and the accumulation of cells in G2/M in both mammalian and yeast cells, effects which are largely dependent on the B55/Cdc55 regulatory subunit of PP2A. Thus, E4orf4 represents a unique means by which the function of a specific form of PP2A can be delineated in vivo. In Saccharomyces cerevisiae, only two PP2A regulatory subunits exist, Cdc55 and Rts1. Here, we show that E4orf4-induced toxicity depends on a functional interaction with Cdc55. E4orf4 expression correlates with the inappropriate reduction of Pds1 and Scc1 in S-phase-arrested cells. The unscheduled loss of these proteins suggests the involvement of PP2ACdc55 in the regulation of the Cdc20 form of the anaphase-promoting complex (APC). Contrastingly, activity of the Hct1 form of the APC is not induced by E4orf4, as demonstrated by the observed stability of its substrates. We propose that E4orf4, being a Cdc55-specific inhibitor of PP2A, demonstrates the role of PP2ACdc55 in regulating APCCdc20 activity.

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Ohi, Ryoma, Anna Feoktistova, Stacey McCann, Virginia Valentine, A. Thomas Look, Joseph S. Lipsick y Kathleen L. Gould. "Myb-Related Schizosaccharomyces pombecdc5p Is Structurally and Functionally Conserved in Eukaryotes". Molecular and Cellular Biology 18, n.º 7 (1 de julio de 1998): 4097–108. http://dx.doi.org/10.1128/mcb.18.7.4097.

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ABSTRACT Schizosaccharomyces pombe cdc5p is a Myb-related protein that is essential for G2/M progression. To explore the structural and functional conservation of Cdc5 throughout evolution, we isolated Cdc5-related genes and cDNAs fromSaccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and Homo sapiens. Supporting the notion that these Cdc5 gene family members are functionally homologous to S. pombe cdc5 +, human and fly Cdc5 cDNAs are capable of complementing the temperature-sensitive lethality of the S. pombe cdc5-120 mutant. Furthermore, S. cerevisiae CEF1(S. cerevisiae homolog of cdc5 +), like S. pombe cdc5 +, is essential during G2/M. The location of the cdc5-120 mutation, as well as mutational analyses of Cef1p, indicate that the Myb repeats of cdc5p and Cef1p are important for their function in vivo. However, we found that unlike in c-Myb, single residue substitutions of glycines for hydrophobic residues within the Myb repeats of Cef1p, which are essential for maintaining structure of the Myb domain, did not impair Cef1p function in vivo. Rather, multiple W-to-G substitutions were required to inactivate Cef1p, and many of the substitution mutants were found to confer temperature sensitivity. Although it is possible that Cef1p acts as a transcriptional activator, we have demonstrated that Cef1p is not involved in transcriptional activation of a class of G2/M-regulated genes typified by SWI5. Collectively, these results suggest that Cdc5 family members participate in a novel pathway to regulate G2/M progression.

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Takeda, Miyoko, Kanako Yamagami y Kazuma Tanaka. "Role of Phosphatidylserine in Phospholipid Flippase-Mediated Vesicle Transport in Saccharomyces cerevisiae". Eukaryotic Cell 13, n.º 3 (3 de enero de 2014): 363–75. http://dx.doi.org/10.1128/ec.00279-13.

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ABSTRACT Phospholipid flippases translocate phospholipids from the exoplasmic to the cytoplasmic leaflet of cell membranes to generate and maintain phospholipid asymmetry. The genome of budding yeast encodes four heteromeric flippases (Drs2p, Dnf1p, Dnf2p, and Dnf3p), which associate with the Cdc50 family noncatalytic subunit, and one monomeric flippase Neo1p. Flippases have been implicated in the formation of transport vesicles, but the underlying mechanisms are largely unknown. We show here that overexpression of the phosphatidylserine synthase gene CHO1 suppresses defects in the endocytic recycling pathway in flippase mutants. This suppression seems to be mediated by increased cellular phosphatidylserine. Two models can be envisioned for the suppression mechanism: (i) phosphatidylserine in the cytoplasmic leaflet recruits proteins for vesicle formation with its negative charge, and (ii) phosphatidylserine flipping to the cytoplasmic leaflet induces membrane curvature that supports vesicle formation. In a mutant depleted for flippases, a phosphatidylserine probe GFP-Lact-C2 was still localized to endosomal membranes, suggesting that the mere presence of phosphatidylserine in the cytoplasmic leaflet is not enough for vesicle formation. The CHO1 overexpression did not suppress the growth defect in a mutant depleted or mutated for all flippases, suggesting that the suppression was dependent on flippase-mediated phospholipid flipping. Endocytic recycling was not blocked in a mutant lacking phosphatidylserine or depleted in phosphatidylethanolamine, suggesting that a specific phospholipid is not required for vesicle formation. These results suggest that flippase-dependent vesicle formation is mediated by phospholipid flipping, not by flipped phospholipids.

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Kitada, K., A. L. Johnson, L. H. Johnston y A. Sugino. "A multicopy suppressor gene of the Saccharomyces cerevisiae G1 cell cycle mutant gene dbf4 encodes a protein kinase and is identified as CDC5." Molecular and Cellular Biology 13, n.º 7 (julio de 1993): 4445–57. http://dx.doi.org/10.1128/mcb.13.7.4445.

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We have isolated a multicopy suppressor of the temperature-sensitive growth phenotype of organisms carrying mutations of DBF4, a gene that is required for the initiation of chromosomal DNA replication in Saccharomyces cerevisiae and that interacts with the CDC7 protein kinase. Nucleotide sequence analysis of the suppressor gene, provisionally named MSD2, revealed an open reading frame encoding a protein with a calculated M(r) of 81,024, with amino acid sequence similarity to the catalytic domains of protein kinases. Both genetic linkage and complementation analyses indicated that MSD2 is identical to the cell division cycle gene CDC5. An activity that phosphorylated exogenously added casein was immunoprecipitated by antiserum against a TrpE-Cdc5 fusion protein from lysates of wild-type cells containing CDC5 on a multicopy plasmid but not of cells bearing a small deletion in the predicted protein kinase domain of CDC5 on the plasmid. Deletion of CDC5 was lethal and resulted in a dumbbell-shaped terminal morphology, with the nuclei almost divided but still connected. Consistent with the function at the G2/M boundary, the CDC5 transcript accumulated periodically during the cell cycle, peaking at the G2/M boundary. CDC5 on a multicopy plasmid also suppresses temperature-sensitive cdc15, cdc20, and dbf2 mutations which affect mitosis during the cell cycle.

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20

Kitada, K., A. L. Johnson, L. H. Johnston y A. Sugino. "A multicopy suppressor gene of the Saccharomyces cerevisiae G1 cell cycle mutant gene dbf4 encodes a protein kinase and is identified as CDC5". Molecular and Cellular Biology 13, n.º 7 (julio de 1993): 4445–57. http://dx.doi.org/10.1128/mcb.13.7.4445-4457.1993.

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We have isolated a multicopy suppressor of the temperature-sensitive growth phenotype of organisms carrying mutations of DBF4, a gene that is required for the initiation of chromosomal DNA replication in Saccharomyces cerevisiae and that interacts with the CDC7 protein kinase. Nucleotide sequence analysis of the suppressor gene, provisionally named MSD2, revealed an open reading frame encoding a protein with a calculated M(r) of 81,024, with amino acid sequence similarity to the catalytic domains of protein kinases. Both genetic linkage and complementation analyses indicated that MSD2 is identical to the cell division cycle gene CDC5. An activity that phosphorylated exogenously added casein was immunoprecipitated by antiserum against a TrpE-Cdc5 fusion protein from lysates of wild-type cells containing CDC5 on a multicopy plasmid but not of cells bearing a small deletion in the predicted protein kinase domain of CDC5 on the plasmid. Deletion of CDC5 was lethal and resulted in a dumbbell-shaped terminal morphology, with the nuclei almost divided but still connected. Consistent with the function at the G2/M boundary, the CDC5 transcript accumulated periodically during the cell cycle, peaking at the G2/M boundary. CDC5 on a multicopy plasmid also suppresses temperature-sensitive cdc15, cdc20, and dbf2 mutations which affect mitosis during the cell cycle.

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21

Wang, Y. y D. J. Burke. "Cdc55p, the B-type regulatory subunit of protein phosphatase 2A, has multiple functions in mitosis and is required for the kinetochore/spindle checkpoint in Saccharomyces cerevisiae." Molecular and Cellular Biology 17, n.º 2 (febrero de 1997): 620–26. http://dx.doi.org/10.1128/mcb.17.2.620.

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Saccharomyces cerevisiae, like most eucaryotic cells, can prevent the onset of anaphase until chromosomes are properly aligned on the mitotic spindle. We determined that Cdc55p (regulatory B subunit of protein phosphatase 2A [PP2A]) is required for the kinetochore/spindle checkpoint regulatory pathway in yeast. ctf13 cdc55 double mutants could not maintain a ctf13-induced mitotic delay, as determined by antitubulin staining and levels of histone H1 kinase activity. In addition, cdc55::LEU2 mutants and tpd3::LEU2 mutants (regulatory A subunit of PP2A) were nocodazole sensitive and exhibited the phenotypes of previously identified kinetochore/spindle checkpoint mutants. Inactivating CDC55 did not simply bypass the arrest that results from inhibiting ubiquitin-dependent proteolysis because cdc16-1 cdc55::LEU2 and cdc23-1 cdc55::LEU2 double mutants arrested normally at elevated temperatures. CDC55 is specific for the kinetochore/spindle checkpoint because cdc55 mutants showed normal sensitivity to gamma radiation and hydroxyurea. The conditional lethality and the abnormal cellular morphogenesis of cdc55::LEU2 were suppressed by cdc28F19, suggesting that the cdc55 phenotypes are dependent on the phosphorylation state of Cdc28p. In contrast, the nocodazole sensitivity of cdc55::LEU2 was not suppressed by cdc28F19. Therefore, the mitotic checkpoint activity of CDC55 (and TPD3) is independent of regulated phosphorylation of Cdc28p. Finally, cdc55::LEU2 suppresses the temperature sensitivity of cdc20-1, suggesting additional roles for CDC55 in mitosis.

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Khondker, Shoily, Sam Kajjo, Devon Chandler-Brown, Jan Skotheim, Adam Rudner y Amy Ikui. "PP2ACdc55 dephosphorylates Pds1 and inhibits spindle elongation in S. cerevisiae". Journal of Cell Science 133, n.º 14 (26 de junio de 2020): jcs243766. http://dx.doi.org/10.1242/jcs.243766.

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ABSTRACTPP2ACdc55 (the form of protein phosphatase 2A containing Cdc55) regulates cell cycle progression by reversing cyclin-dependent kinase (CDK)- and polo-like kinase (Cdc5)-dependent phosphorylation events. In S. cerevisiae, Cdk1 phosphorylates securin (Pds1), which facilitates Pds1 binding and inhibits separase (Esp1). During anaphase, Esp1 cleaves the cohesin subunit Scc1 and promotes spindle elongation. Here, we show that PP2ACdc55 directly dephosphorylates Pds1 both in vivo and in vitro. Pds1 hyperphosphorylation in a cdc55 deletion mutant enhanced the Pds1–Esp1 interaction, which played a positive role in Pds1 nuclear accumulation and in spindle elongation. We also show that nuclear PP2ACdc55 plays a role during replication stress to inhibit spindle elongation. This pathway acted independently of the known Mec1, Swe1 or spindle assembly checkpoint (SAC) checkpoint pathways. We propose a model where Pds1 dephosphorylation by PP2ACdc55 disrupts the Pds1–Esp1 protein interaction and inhibits Pds1 nuclear accumulation, which prevents spindle elongation, a process that is elevated during replication stress.

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23

Ahn, Jae-Woo, Sangwoo Kim, Eun-Jung Kim, Yeo-Jin Kim y Kyung-Jin Kim. "Structural insights into the novel ARM-repeat protein CTNNBL1 and its association with the hPrp19–CDC5L complex". Acta Crystallographica Section D Biological Crystallography 70, n.º 3 (22 de febrero de 2014): 780–88. http://dx.doi.org/10.1107/s139900471303318x.

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The hPrp19–CDC5L complex plays a crucial role during human pre-mRNA splicing by catalytic activation of the spliceosome. In order to elucidate the molecular architecture of the hPrp19–CDC5L complex, the crystal structure of CTNNBL1, one of the major components of this complex, was determined. Unlike canonical ARM-repeat proteins such as β-catenin and importin-α, CTNNBL1 was found to contain a twisted and extended ARM-repeat structure at the C-terminal domain and, more importantly, the protein formed a stable dimer. A highly negatively charged patch formed in the N-terminal ARM-repeat domain of CTNNBL1 provides a binding site for CDC5L, a binding partner of the protein in the hPrp19–CDC5L complex, and these two proteins form a complex with a stoichiometry of 2:2. These findings not only present the crystal structure of a novel ARM-repeat protein, CTNNBL1, but also provide insights into the detailed molecular architecture of the hPrp19–CDC5L complex.

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24

Rossio, Valentina y Satoshi Yoshida. "Spatial regulation of Cdc55–PP2A by Zds1/Zds2 controls mitotic entry and mitotic exit in budding yeast". Journal of Cell Biology 193, n.º 3 (2 de mayo de 2011): 445–54. http://dx.doi.org/10.1083/jcb.201101134.

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Budding yeast CDC55 encodes a regulatory B subunit of the PP2A (protein phosphatase 2A), which plays important roles in mitotic entry and mitotic exit. The spatial and temporal regulation of PP2A is poorly understood, although recent studies demonstrated that the conserved proteins Zds1 and Zds2 stoichiometrically bind to Cdc55–PP2A and regulate it in a complex manner. Zds1/Zds2 promote Cdc55–PP2A function for mitotic entry, whereas Zds1/Zds2 inhibit Cdc55–PP2A function during mitotic exit. In this paper, we propose that Zds1/Zds2 primarily control Cdc55 localization. Cortical and cytoplasmic localization of Cdc55 requires Zds1/Zds2, and Cdc55 accumulates in the nucleus in the absence of Zds1/Zds2. By genetically manipulating the nucleocytoplasmic distribution of Cdc55, we showed that Cdc55 promotes mitotic entry when in the cytoplasm. On the other hand, nuclear Cdc55 prevents mitotic exit. Our analysis defines the long-sought molecular function for the zillion different screens family proteins and reveals the importance of the regulation of PP2A localization for proper mitotic progression.

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25

Grote, Michael, Elmar Wolf, Cindy L. Will, Ira Lemm, Dmitry E. Agafonov, Adrian Schomburg, Wolfgang Fischle, Henning Urlaub y Reinhard Lührmann. "Molecular Architecture of the Human Prp19/CDC5L Complex". Molecular and Cellular Biology 30, n.º 9 (22 de febrero de 2010): 2105–19. http://dx.doi.org/10.1128/mcb.01505-09.

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ABSTRACT Protein complexes containing Prp19 play a central role during catalytic activation of the spliceosome, and Prp19 and its related proteins are major components of the spliceosome's catalytic core RNP. To learn more about the spatial organization of the human Prp19 (hPrp19)/CDC5L complex, which is comprised of hPrp19, CDC5L, PRL1, AD002, SPF27, CTNNBL1, and HSP73, we purified native hPrp19/CDC5L complexes from HeLa cells stably expressing FLAG-tagged AD002 or SPF27. Stoichiometric analyses indicated that, like Saccharomyces cerevisiae NTC ( n ine t een c omplex), the human Prp19/CDC5L complex contains four copies of hPrp19. Salt treatment identified a stable core comprised of CDC5L, hPrp19, PRL1, and SPF27. Protein-protein interaction studies revealed that SPF27 directly interacts with each component of the hPrp19/CDC5L complex core and also elucidated several additional, previously unknown interactions between hPrp19/CDC5L complex components. Limited proteolysis of the hPrp19/CDC5L complex revealed a protease-resistant complex comprised of SPF27, the C terminus of CDC5L, and the N termini of PRL1 and hPrp19. Under the electron microscope, purified hPrp19/CDC5L complexes exhibit an elongated, asymmetric shape with a maximum dimension of ∼20 nm. Our findings not only elucidate the molecular organization of the hPrp19/CDC5L complex but also provide insights into potential protein-protein interactions at the core of the catalytically active spliceosome.

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26

Kishimoto, Takuma, Takaharu Yamamoto y Kazuma Tanaka. "Defects in Structural Integrity of Ergosterol and the Cdc50p-Drs2p Putative Phospholipid Translocase Cause Accumulation of Endocytic Membranes, onto Which Actin Patches Are Assembled in Yeast". Molecular Biology of the Cell 16, n.º 12 (diciembre de 2005): 5592–609. http://dx.doi.org/10.1091/mbc.e05-05-0452.

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Specific changes in membrane lipid composition are implicated in actin cytoskeletal organization, vesicle formation, and control of cell polarity. Cdc50p, a membrane protein in the endosomal/trans-Golgi network compartments, is a noncatalytic subunit of Drs2p, which is implicated in translocation of phospholipids across lipid bilayers. We found that the cdc50Δ mutation is synthetically lethal with mutations affecting the late steps of ergosterol synthesis (erg2 to erg6). Defects in cell polarity and actin organization were observed in the cdc50Δ erg3Δ mutant. In particular, actin patches, which are normally found at cortical sites, were assembled intracellularly along with their assembly factors, including Las17p, Abp1p, and Sla2p. The exocytic SNARE Snc1p, which is recycled by an endocytic route, was also intracellularly accumulated, and inhibition of endocytic internalization suppressed the cytoplasmic accumulation of both Las17p and Snc1p. Simultaneous loss of both phospholipid asymmetry and sterol structural integrity could lead to accumulation of endocytic intermediates capable of initiating assembly of actin patches in the cytoplasm.

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27

Willems, A. R., T. Goh, L. Taylor, I. Chernushevich, A. Shevchenko y M. Tyers. "SCF ubiquitin protein ligases and phosphorylation–dependent proteolysis". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 354, n.º 1389 (29 de septiembre de 1999): 1533–50. http://dx.doi.org/10.1098/rstb.1999.0497.

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Many key activators and inhibitors of cell division are targeted for degradation by a recently described family of E3 ubiquitin protein ligases termed Skp1–Cdc53–F–box protein (SCF) complexes. SCF complexes physically link substrate proteins to the E2 ubiquitin–conjugating enzyme Cdc34, which catalyses substrate ubiquitination, leading to subsequent degradation by the 26S proteasome. SCF complexes contain a variable subunit called an F–box protein that confers substrate specificity on an invariant core complex composed of the subunits Cdc34, Skp1 and Cdc53. Here, we review the substrates and pathways regulated by the yeast F–box proteins Cdc4, Grr1 and Met30. The concepts of SCF ubiquitin ligase function are illustrated by analysis of the degradation pathway for the G1 cyclin Cln2. Through mass spectrometric analysis of Cdc53 associated proteins, we have identified three novel F–box proteins that appear to participate in SCF–like complexes. As many F–box proteins can be found in sequence databases, it appears that a host of cellular pathways will be regulated by SCF–dependent proteolysis.

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28

Connors, Bernadette, Lauren Rochelle, Asela Roberts y Graham Howard. "A Synthetic Interaction between CDC20 and RAD4 in Saccharomyces cerevisiae upon UV Irradiation". Molecular Biology International 2014 (23 de febrero de 2014): 1–8. http://dx.doi.org/10.1155/2014/519290.

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Regulation of DNA repair can be achieved through ubiquitin-mediated degradation of transiently induced proteins. In Saccharomyces cerevisiae, Rad4 is involved in damage recognition during nucleotide excision repair (NER) and, in conjunction with Rad23, recruits other proteins to the site of damage. We identified a synthetic interaction upon UV exposure between Rad4 and Cdc20, a protein that modulates the activity of the anaphase promoting complex (APC/C), a multisubunit E3 ubiquitin ligase complex. The moderately UV sensitive Δrad4 strain became highly sensitive when cdc20-1 was present, and was rescued by overexpression of CDC20. The double mutant is also deficient in elicting RNR3-lacZ transcription upon exposure to UV irradiation or 4-NQO compared with the Δrad4 single mutant. We demonstrate that the Δrad4/cdc20-1 double mutant is defective in double strand break repair by way of a plasmid end-joining assay, indicating that Rad4 acts to ensure that damaged DNA is repaired via a Cdc20-mediated mechanism. This study is the first to present evidence that Cdc20 may play a role in the degradation of proteins involved in nucleotide excision repair.

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29

Leslie, Mitch. "Proteins keep Cdc55 in its place". Journal of Cell Biology 193, n.º 3 (2 de mayo de 2011): 426. http://dx.doi.org/10.1083/jcb.1933iti1.

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30

Gao, Yang, Pengbo Wen, Bin Chen, Guanshuo Hu, Lijun Wu, An Xu y Guoping Zhao. "Downregulation of CDC20 Increases Radiosensitivity through Mcl-1/p-Chk1-Mediated DNA Damage and Apoptosis in Tumor Cells". International Journal of Molecular Sciences 21, n.º 18 (12 de septiembre de 2020): 6692. http://dx.doi.org/10.3390/ijms21186692.

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Radiotherapy is an important modality for the local control of human cancers, but the radioresistance induced by aberrant apoptotic signaling is a hallmark of cancers. Restoring the aberrant apoptotic pathways is an emerging strategy for cancer radiotherapy. In this study, we determined that targeting cell division cycle 20 (CDC20) radiosensitized colorectal cancer (CRC) cells through mitochondrial-dependent apoptotic signaling. CDC20 was overexpressed in CRC cells and upregulated after radiation. Inhibiting CDC20 activities genetically or pharmacologically suppressed the proliferation and increased radiation-induced DNA damage and intrinsic apoptosis in CRC cells. Mechanistically, knockdown of CDC20 suppressed the expression of antiapoptotic protein Mcl-1 but not other Bcl-2 family proteins. The expressions of CDC20 and Mcl-1 respond to radiation simultaneously through direct interaction, as evidenced by immunoprecipitation and glutathione S-transferase (GST) pull-down assays. Subsequently, decreased Mcl-1 expression inhibited the expression level of phosphorylated checkpoint kinase 1 (p-Chk1), thereby resulting in impaired DNA damage repair through downregulating the homologous recombination repair protein Rad51 and finally causing apoptotic signaling. In addition, both CDC20 and Chk1 inhibitors together, through in vivo studies, confirmed the radiosensitizing effect of CDC20 via inhibiting Mcl-1 and p-Chk1 expression. In summary, our results indicate that targeting CDC20 is a promising strategy to improve cancer radiotherapy.

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31

Di Fiore, Barbara y Jonathon Pines. "How cyclin A destruction escapes the spindle assembly checkpoint". Journal of Cell Biology 190, n.º 4 (23 de agosto de 2010): 501–9. http://dx.doi.org/10.1083/jcb.201001083.

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The anaphase-promoting complex/cyclosome (APC/C) is the ubiquitin ligase essential to mitosis, which ensures that specific proteins are degraded at specific times to control the order of mitotic events. The APC/C coactivator, Cdc20, is targeted by the spindle assembly checkpoint (SAC) to restrict APC/C activity until metaphase, yet early substrates, such as cyclin A, are degraded in the presence of the active checkpoint. Cdc20 and the cyclin-dependent kinase cofactor, Cks, are required for cyclin A destruction, but how they enable checkpoint-resistant destruction has not been elucidated. In this study, we answer this problem: we show that the N terminus of cyclin A binds directly to Cdc20 and with sufficient affinity that it can outcompete the SAC proteins. Subsequently, the Cks protein is necessary and sufficient to promote cyclin A degradation in the presence of an active checkpoint by binding cyclin A–Cdc20 to the APC/C.

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32

Mathias, N., S. L. Johnson, M. Winey, A. E. Adams, L. Goetsch, J. R. Pringle, B. Byers y M. G. Goebl. "Cdc53p acts in concert with Cdc4p and Cdc34p to control the G1-to-S-phase transition and identifies a conserved family of proteins." Molecular and Cellular Biology 16, n.º 12 (diciembre de 1996): 6634–43. http://dx.doi.org/10.1128/mcb.16.12.6634.

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Regulation of cell cycle progression occurs in part through the targeted degradation of both activating and inhibitory subunits of the cyclin-dependent kinases. During G1, CDC4, encoding a WD-40 repeat protein, and CDC34, encoding a ubiquitin-conjugating enzyme, are involved in the destruction of these regulators. Here we describe evidence indicating that CDC53 also is involved in this process. Mutations in CDC53 cause a phenotype indistinguishable from those of cdc4 and cdc34 mutations, numerous genetic interactions are seen between these genes, and the encoded proteins are found physically associated in vivo. Cdc53p defines a large family of proteins found in yeasts, nematodes, and humans whose molecular functions are uncharacterized. These results suggest a role for this family of proteins in regulating cell cycle proliferation through protein degradation.

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Kramer, Edgar R., Nadja Scheuringer, Alexandre V. Podtelejnikov, Matthias Mann y Jan-Michael Peters. "Mitotic Regulation of the APC Activator Proteins CDC20 and CDH1". Molecular Biology of the Cell 11, n.º 5 (mayo de 2000): 1555–69. http://dx.doi.org/10.1091/mbc.11.5.1555.

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The ordered activation of the ubiquitin protein ligase anaphase-promoting complex (APC) or cyclosome by CDC20 in metaphase and by CDH1 in telophase is essential for anaphase and for exit from mitosis, respectively. Here, we show that CDC20 can only bind to and activate the mitotically phosphorylated form of theXenopus and the human APC in vitro. In contrast, the analysis of phosphorylated and nonphosphorylated forms of CDC20 suggests that CDC20 phosphorylation is neither sufficient nor required for APC activation. On the basis of these results and the observation that APC phosphorylation correlates with APC activation in vivo, we propose that mitotic APC phosphorylation is an important mechanism that controls the proper timing of APCCDC20 activation. We further show that CDH1 is phosphorylated in vivo during S, G2, and M phase and that CDH1 levels fluctuate during the cell cycle. In vitro, phosphorylated CDH1 neither binds to nor activates the APC as efficiently as does nonphosphorylated CDH1. Nonphosphorylatable CDH1 mutants constitutively activate APC in vitro and in vivo, whereas mutants mimicking the phosphorylated form of CDH1 are constitutively inactive. These results suggest that mitotic kinases have antagonistic roles in regulating APCCDC20 and APCCDH1; the phosphorylation of APC subunits is required to allow APC activation by CDC20, whereas the phosphorylation of CDH1 prevents activation of the APC by CDH1. These mechanisms can explain the temporal order of APC activation by CDC20 and CDH1 and may help to ensure that exit from mitosis is not initiated before anaphase has occurred.

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Flescher, EG, K. Madden y M. Snyder. "Components required for cytokinesis are important for bud site selection in yeast". Journal of Cell Biology 122, n.º 2 (15 de julio de 1993): 373–86. http://dx.doi.org/10.1083/jcb.122.2.373.

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Polarized cell division is a fundamental process that occurs in a variety of organisms; it is responsible for the proper positioning of daughter cells and the correct segregation of cytoplasmic components. The SPA2 gene of yeast encodes a nonessential protein that localizes to sites of cell growth and to the site of cytokinesis. spa2 mutants exhibit slightly altered budding patterns. In this report, a genetic screen was used to isolate a novel ochre allele of CDC10, cdc10-10; strains containing this mutation require the SPA2 gene for growth. CDC10 encodes a conserved potential GTP-binding protein that previously has been shown to localize to the bud neck and to be important for cytokinesis. The genetic interaction of cdc10-10 and spa2 suggests a role for SPA2 in cytokinesis. Most importantly, strains that contain a cdc10-10 mutation and those containing mutations affecting other putative neck filament proteins do not form buds at their normal proximal location. The finding that a component involved in cytokinesis is also important in bud site selection provides strong evidence for the cytokinesis tag model; i.e., critical components at the site of cytokinesis are involved in determining the next site of polarized growth and division.

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35

Nath, Somsubhra, Abhishek Chowdhury, Sanjib Dey, Anirban Roychoudhury, Abira Ganguly, Dibyendu Bhattacharyya y Susanta Roychoudhury. "Deregulation of Rb-E2F1 Axis Causes Chromosomal Instability by Engaging the Transactivation Function of Cdc20–Anaphase-Promoting Complex/Cyclosome". Molecular and Cellular Biology 35, n.º 2 (3 de noviembre de 2014): 356–69. http://dx.doi.org/10.1128/mcb.00868-14.

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The E2F family of transcription factors regulates genes involved in various aspects of the cell cycle. Beyond the well-documented role in G1/S transition, mitotic regulation by E2F has also been reported. Proper mitotic progression is monitored by the spindle assembly checkpoint (SAC). The SAC ensures bipolar separation of chromosomes and thus prevents aneuploidy. There are limited reports on the regulation of the SAC by E2F. Our previous work identified the SAC protein Cdc20 as a novel transcriptional regulator of the mitotic ubiquitin carrier protein UbcH10. However, none of the Cdc20 transcription complex proteins have any known DNA binding domain. Here we show that an E2F1-DP1 heterodimer is involved in recruitment of the Cdc20 transcription complex to theUBCH10promoter and in transactivation of the gene. We further show that inactivation of Rb can facilitate this transactivation process. Moreover, this E2F1-mediated regulation of UbcH10 influences mitotic progression. Deregulation of this pathway results in premature anaphase, chromosomal abnormalities, and aneuploidy. We conclude that excess E2F1 due to Rb inactivation recruits the complex of Cdc20 and the anaphase-promoting complex/cyclosome (Cdc20-APC/C) to deregulate the expression ofUBCH10, leading to chromosomal instability in cancer cells.

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36

Piano, Valentina, Amal Alex, Patricia Stege, Stefano Maffini, Gerardo A. Stoppiello, Pim J. Huis in ’t Veld, Ingrid R. Vetter y Andrea Musacchio. "CDC20 assists its catalytic incorporation in the mitotic checkpoint complex". Science 371, n.º 6524 (31 de diciembre de 2020): 67–71. http://dx.doi.org/10.1126/science.abc1152.

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Open (O) and closed (C) topologies of HORMA-domain proteins are respectively associated with inactive and active states of fundamental cellular pathways. The HORMA protein O-MAD2 converts to C-MAD2 upon binding CDC20. This is rate limiting for assembly of the mitotic checkpoint complex (MCC), the effector of a checkpoint required for mitotic fidelity. A catalyst assembled at kinetochores accelerates MAD2:CDC20 association through a poorly understood mechanism. Using a reconstituted SAC system, we discovered that CDC20 is an impervious substrate for which access to MAD2 requires simultaneous docking on several sites of the catalytic complex. Our analysis indicates that the checkpoint catalyst is substrate assisted and promotes MCC assembly through spatially and temporally coordinated conformational changes in both MAD2 and CDC20. This may define a paradigm for other HORMA-controlled systems.

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37

Lei, X. H., X. Shen, X. Q. Xu y H. S. Bernstein. "Human Cdc5, a regulator of mitotic entry, can act as a site-specific DNA binding protein". Journal of Cell Science 113, n.º 24 (15 de diciembre de 2000): 4523–31. http://dx.doi.org/10.1242/jcs.113.24.4523.

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G(2)/M progression requires coordinated expression of many gene products, but little is known about the transcriptional regulators involved. We recently identified human Cdc5, a positive regulator of G(2)/M in mammalian cells. We also demonstrated the presence of a latent activation domain in its carboxyl terminus, suggesting that human Cdc5 regulates G(2)/M through transcriptional activation. Despite the presence of a DNA binding domain, studies by others have failed to identify a preferential binding site for Cdc5 family members. In addition, Cdc5 recently has been associated with the splicesome in several organisms, suggesting that it may not act through DNA binding. We now report the identification of a 12 bp sequence to which human Cdc5 binds specifically and with high affinity through its amino terminus. We show that this DNA-protein interaction is capable of activating transcription. We also used a selection system in yeast to identify human genomic fragments that interact with human Cdc5. Several of these contained sequences similar to the binding site. We demonstrate that these bind human Cdc5 with similar specificity and affinity. These experiments provide the first evidence that Cdc5 family members can act as site-specific DNA binding proteins, and that human Cdc5 may interact with specific, low abundance sequences in the human genome. This raises the possibility that Cdc5 proteins may participate in more than one process necessary for regulated cell division.

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38

Yellman, Christopher M. y Daniel J. Burke. "The Role of Cdc55 in the Spindle Checkpoint Is through Regulation of Mitotic Exit in Saccharomyces cerevisiae". Molecular Biology of the Cell 17, n.º 2 (febrero de 2006): 658–66. http://dx.doi.org/10.1091/mbc.e05-04-0336.

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Cdc55, a B-type regulatory subunit of protein phosphatase 2A, has been implicated in mitotic spindle checkpoint activity and maintenance of sister chromatid cohesion during metaphase. The spindle checkpoint is composed of two independent pathways, one leading to inhibition of the metaphase-to-anaphase transition by checkpoint proteins, including Mad2, and the other to inhibition of mitotic exit by Bub2. We show that Cdc55 is a negative regulator of mitotic exit. A cdc55 mutant, like a bub2 mutant, prematurely releases Cdc14 phosphatase from the nucleolus during spindle checkpoint activation, and premature exit from mitosis indirectly leads to loss of sister chromatid cohesion and inviability in nocodazole. The role of Cdc55 is separable from Bub2 and inhibits release of Cdc14 through a mechanism independent of the known negative regulators of mitotic exit. Epistasis experiments indicate Cdc55 acts either downstream or independent of the mitotic exit network kinase Cdc15. Interestingly, the B-type cyclin Clb2 is partially stable during premature activation of mitotic exit in a cdc55 mutant, indicating mitotic exit is incomplete.

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39

Vigneron, Suzanne, Susana Prieto, Cyril Bernis, Jean-Claude Labbé, Anna Castro y Thierry Lorca. "Kinetochore Localization of Spindle Checkpoint Proteins: Who Controls Whom?" Molecular Biology of the Cell 15, n.º 10 (octubre de 2004): 4584–96. http://dx.doi.org/10.1091/mbc.e04-01-0051.

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The spindle checkpoint prevents anaphase onset until all the chromosomes have successfully attached to the spindle microtubules. The mechanisms by which unattached kinetochores trigger and transmit a primary signal are poorly understood, although it seems to be dependent at least in part, on the kinetochore localization of the different checkpoint components. By using protein immunodepletion and mRNA translation in Xenopus egg extracts, we have studied the hierarchic sequence and the interdependent network that governs protein recruitment at the kinetochore in the spindle checkpoint pathway. Our results show that the first regulatory step of this cascade is defined by Aurora B/INCENP complex. Aurora B/INCENP controls the activation of a second regulatory level by inducing at the kinetochore the localization of Mps1, Bub1, Bub3, and CENP-E. This localization, in turn, promotes the recruitment to the kinetochore of Mad1/Mad2, Cdc20, and the anaphase promoting complex (APC). Unlike Aurora B/INCENP, Mps1, Bub1, and CENP-E, the downstream checkpoint protein Mad1 does not regulate the kinetochore localization of either Cdc20 or APC. Similarly, Cdc20 and APC do not require each other to be localized at these chromosome structures. Thus, at the last step of the spindle checkpoint cascade, Mad1/Mad2, Cdc20, and APC are recruited at the kinetochores independently from each other.

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40

Poddar, Atasi, P. Todd Stukenberg y Daniel J. Burke. "Two Complexes of Spindle Checkpoint Proteins Containing Cdc20 and Mad2 Assemble during Mitosis Independently of the Kinetochore in Saccharomyces cerevisiae". Eukaryotic Cell 4, n.º 5 (mayo de 2005): 867–78. http://dx.doi.org/10.1128/ec.4.5.867-878.2005.

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ABSTRACT Favored models of spindle checkpoint signaling propose that two inhibitory complexes (Mad2-Cdc20 and Mad2-Mad3-Bub3-Cdc20) must be assembled at kinetochores in order to inhibit mitosis. We have directly tested this model in the budding yeast Saccharomyces cerevisiae. The proteins Mad2, Mad3, Bub3, Cdc20, and Cdc27 in yeast were quantified, and there are sufficient amounts to form stoichiometric inhibitors of Cdc20 and the anaphase-promoting complex. Mad2 is present in two separate complexes in cells arrested in mitosis with nocodazole. There is a small amount of Mad2-Mad3-Bub3-Cdc20 and a much larger amount of a complex that contains Mad2-Cdc20. We use conditional mutants to show that both Mad2 and Mad3 are essential for establishment and maintenance of the spindle checkpoint. Both spindle checkpoint complexes containing Mad2 form in mitosis, not in response to checkpoint activation. The kinetochore is not required to form either complex. We propose that the conversion of Mad1-Mad2 to Cdc20-Mad2, a key step in generating inhibitory checkpoint complexes, is limited to mitosis by the availability of Cdc20 and is kinetochore independent.

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41

Whitehall, Simon, Peter Stacey, Keren Dawson y Nic Jones. "Cell Cycle–regulated Transcription in Fission Yeast: Cdc10–Res Protein Interactions during the Cell Cycle and Domains Required for Regulated Transcription". Molecular Biology of the Cell 10, n.º 11 (noviembre de 1999): 3705–15. http://dx.doi.org/10.1091/mbc.10.11.3705.

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In Schizosaccharomyces pombe the MBF (DSC1) complex mediates transcriptional activation at Start and is composed of a common subunit called Cdc10 in combination with two alternative DNA-binding partners, Res1 and Res2. It has been suggested that a high-activity MBF complex (at G1/S) is switched to a low-activity complex (in G2) by the incorporation of the negative regulatory subunit Res2. We have analyzed MBF protein–protein interactions and find that both Res proteins are associated with Cdc10 throughout the cell cycle, arguing against this model. Furthermore we demonstrate that Res2 is capable of interacting with a mutant form of Cdc10 that has high transcriptional activity. It has been shown previously that both Res proteins are required for periodic cell cycle–regulated transcription. Therefore a series of Res1–Res2 hybrid molecules was used to determine the domains that are specifically required to regulate periodic transcription. In Res2 the nature of the C-terminal region is critical, and in both Res1 and Res2, a domain overlapping the N-terminal ankyrin repeat and a recently identified activation domain is important for mediating cell cycle–regulated transcription.

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42

Ben-Yehuda, Sigal, Ian Dix, Caroline S. Russell, Margaret McGarvey, Jean D. Beggs y Martin Kupiec. "Genetic and Physical Interactions Between Factors Involved in Both Cell Cycle Progression and Pre-mRNA Splicing inSaccharomyces cerevisiae". Genetics 156, n.º 4 (1 de diciembre de 2000): 1503–17. http://dx.doi.org/10.1093/genetics/156.4.1503.

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AbstractThe PRP17/CDC40 gene of Saccharomyces cerevisiae functions in two different cellular processes: pre-mRNA splicing and cell cycle progression. The Prp17/Cdc40 protein participates in the second step of the splicing reaction and, in addition, prp17/cdc40 mutant cells held at the restrictive temperature arrest in the G2 phase of the cell cycle. Here we describe the identification of nine genes that, when mutated, show synthetic lethality with the prp17/cdc40Δ allele. Six of these encode known splicing factors: Prp8p, Slu7p, Prp16p, Prp22p, Slt11p, and U2 snRNA. The other three, SYF1, SYF2, and SYF3, represent genes also involved in cell cycle progression and in pre-mRNA splicing. Syf1p and Syf3p are highly conserved proteins containing several copies of a repeated motif, which we term RTPR. This newly defined motif is shared by proteins involved in RNA processing and represents a subfamily of the known TPR (tetratricopeptide repeat) motif. Using two-hybrid interaction screens and biochemical analysis, we show that the SYF gene products interact with each other and with four other proteins: Isy1p, Cef1p, Prp22p, and Ntc20p. We discuss the role played by these proteins in splicing and cell cycle progression.

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43

DeAntoni, Anna, Valeria Sala y Andrea Musacchio. "Explaining the oligomerization properties of the spindle assembly checkpoint protein Mad2". Philosophical Transactions of the Royal Society B: Biological Sciences 360, n.º 1455 (29 de marzo de 2005): 637–48. http://dx.doi.org/10.1098/rstb.2004.1618.

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Mad2 is an essential component of the spindle assembly checkpoint (SAC), a molecular device designed to coordinate anaphase onset with the completion of chromosome attachment to the spindle. Capture of chromosome by microtubules occur on protein scaffolds known as kinetochores. The SAC proteins are recruited to kinetochores in prometaphase where they generate a signal that halts anaphase until all sister chromatid pairs are bipolarly oriented. Mad2 is a subunit of the mitotic checkpoint complex, which is regarded as the effector of the spindle checkpoint. Its function is the sequestration of Cdc20, a protein required for progression into anaphase. The function of Mad2 in the checkpoint correlates with a dramatic conformational rearrangement of the Mad2 protein. Mad2 adopts a closed conformation (C-Mad2) when bound to Cdc20, and an open conformation (O-Mad2) when unbound to this ligand. Checkpoint activation promotes the conversion of O-Mad2 to Cdc20-bound C-Mad2. We show that this conversion requires a C-Mad2 template and we identify this in Mad1-bound Mad2. In our proposition, Mad1-bound C-Mad2 recruits O-Mad2 to kinetochores, stimulating Cdc20 capture, implying that O-Mad2 and C-Mad2 form dimers. We discuss Mad2 oligomerization and link our discoveries to previous observations related to Mad2 oligomerization.

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44

Li, Min, J. Philippe York y Pumin Zhang. "Loss of Cdc20 Causes a Securin-Dependent Metaphase Arrest in Two-Cell Mouse Embryos". Molecular and Cellular Biology 27, n.º 9 (26 de febrero de 2007): 3481–88. http://dx.doi.org/10.1128/mcb.02088-06.

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ABSTRACT The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase mediating targeted proteolysis through ubiquitination of protein substrates to control the progression of mitosis. The APC/C recognizes its substrates through two adapter proteins, Cdc20 and Cdh1, which contain similar C-terminal domains composed of seven WD-40 repeats believed to be involved in interacting with their substrates. During the transition from metaphase to anaphase, APC/C-Cdc20 mediates the ubiquitination of securin and cyclin B1, allowing the activation of separase and the onset of anaphase and mitotic exit. APC/C-Cdc20 and APC/C-Cdh1 have overlapping substrates. It is unclear whether they are redundant for mitosis. Using a gene-trapping approach, we have obtained mice which lack Cdc20 function. These mice show failed embryogenesis. The embryos were arrested in metaphase at the two-cell stage with high levels of cyclin B1, indicating an essential role of Cdc20 in mitosis that is not redundant with that of Cdh1. Interestingly, Cdc20 and securin double mutant embryos could not maintain the metaphase arrest, suggesting a role of securin in preventing mitotic exit.

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45

Tavormina, Penny A. y Daniel J. Burke. "Cell Cycle Arrest in cdc20 Mutants of Saccharomyces cerevisiae Is Independent of Ndc10p and Kinetochore Function but Requires a Subset of Spindle Checkpoint Genes". Genetics 148, n.º 4 (1 de abril de 1998): 1701–13. http://dx.doi.org/10.1093/genetics/148.4.1701.

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Abstract The spindle checkpoint ensures accurate chromosome segregation by inhibiting anaphase onset in response to altered microtubule function and impaired kinetochore function. In this study, we report that the ability of the anti-microtubule drug nocodazole to inhibit cell cycle progression in Saccharomyces cerevisiae depends on the function of the kinetochore protein encoded by NDC10. We examined the role of the spindle checkpoint in the arrest in cdc20 mutants that arrest prior to anaphase with an aberrant spindle. The arrest in cdc20 defective cells is dependent on the BUB2 checkpoint and independent of the BUB1, BUB3, and MAD spindle checkpoint genes. We show that the lesion recognized by Bub2p is not excess microtubules, and the cdc20 arrest is independent of kinetochore function. We show that Cdc20p is not required for cyclin proteolysis at two points in the cell cycle, suggesting that CDC20 is distinct from genes encoding integral proteins of the anaphase promoting complex.

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46

Gordienko, I. M., L. M. Shlapatska, L. M. Kovalevska y S. P. Sidorenko. "DIFFERENTIAL EXPRESSION OF CD150/SLAMF1 IN NORMAL AND MALIGNANT B CELLS ON THE DIFFERENT STAGES OF MATURATION". Experimental Oncology 38, n.º 2 (22 de junio de 2016): 101–7. http://dx.doi.org/10.31768/2312-8852.2016.38(2):101-107.

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Background: Within B-cell lineage cell surface receptor CD150/SLAMF1 is broadly expressed starting from pre-B cells with upregulation toward plasma cells. However, expression of CD150 is rather limited on the surface of malignant B cells with the block of differentiation at the different stages of maturation. The aim of our work was to explore CD150 expression both on protein and mRNA levels with the emphasis on CD150 isoforms in malignant B-cell lines at the different stages of maturation in comparison with their normal B cell counterparts. Materials and Methods: Studies were performed on normal tonsillar B-cell subpopulations, Blymphoblastoid cell lines, malignant B-cell lines of different origin, including pre-B acute lymphoblastic leukemia, Burkitt’s lymphoma, Hodgkin’s lymphoma, and multiple myeloma. Protein CD150 expression was assessed by western blot analysis and the expression level of CD150 isoforms was evaluated using qRT-PCR. Results: Despite the similar CD150 expression both on mRNA and protein levels in normal B-cell subsets and B-lymphoblastoid cell lines, malignant B-cell lines demonstrated substantial heterogeneity in CD150 expression. Only Hodgkin’s lymphoma cell lines, Burkitt’s lymphoma cell lines BJAB and Raji, and also pre-B cell line BLIN-1 expressed CD150 protein. At the same time total CD150 and mCD150 mRNA was detected in all studied cell lines excluding pre-B cell line REH. The minor sCD150 isoform was found only in Hodgkin’s lymphoma cell lines and Burkitt’s lymphoma cell line Raji. The nCD150 isoform was broadly expressed in tested B cell lines with exception of REH and Daudi. Conclusion: Malignant Bcell lines at the different stages of maturation only partially resemble their normal counterparts by CD150 expression. In malignant B-cell lines, CD150 expression on mRNA level is much broader than on protein level. CD150 isoforms are differentially expressed in normal and malignant B cells with predominant expression of mCD150 isoform.

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47

Connolly, T., M. Caligiuri y D. Beach. "The Cdc2 protein kinase controls Cdc10/Sct1 complex formation." Molecular Biology of the Cell 8, n.º 6 (junio de 1997): 1105–15. http://dx.doi.org/10.1091/mbc.8.6.1105.

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In the fission yeast Schizosaccharomyces pombe, the execution of Start requires the activity of the Cdc2 protein kinase and the Cdc10/Sct1 transcription complex. The loss of any of these genes leads to G1 arrest and activation of the mating pathway under appropriate conditions. We have undertaken a genetic and biochemical analysis of these genes and their protein products to elucidate the molecular mechanism that governs the regulation of Start. We demonstrate that serine-196 of Cdc10 is phosphorylated in vivo and provide evidence that suggests that phosphorylation of this residue is required for Cdc10 function. Substitution of serine-196 of Cdc10 with alanine (Cdc10 S196A) leads to inactivation of Cdc10. We show that Cdc10 S196A is incapable of associating with Sct1 to form a heteromeric complex, whereas substitution of this serine with aspartic acid (S196D) restores DNA-binding activity by allowing Cdc10 to associate with Sct1. Furthermore, we demonstrate that Cdc2 activity is required for the formation of the heteromeric Sct1/Cdc10 transcription complex and that the Cdc10 S196D mutation alleviates this requirement. We thus provide biochemical evidence to demonstrate one mechanism by which the Cdc2 protein kinase may regulate Start in the fission yeast cell cycle.

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48

Shen, Wen-Hui, Yves Parmentier, Hanjo Hellmann, Esther Lechner, Aiwu Dong, Jean Masson, Fabienne Granier, Loı̈c Lepiniec, Mark Estelle y Pascal Genschik. "Null Mutation of AtCUL1 Causes Arrest in Early Embryogenesis in Arabidopsis". Molecular Biology of the Cell 13, n.º 6 (junio de 2002): 1916–28. http://dx.doi.org/10.1091/mbc.e02-02-0077.

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The SCF (for SKP1, Cullin/CDC53,F-box protein) ubiquitin ligase targets a number of cell cycle regulators, transcription factors, and other proteins for degradation in yeast and mammalian cells. Recent genetic studies demonstrate that plant F-box proteins are involved in auxin responses, jasmonate signaling, flower morphogenesis, photocontrol of circadian clocks, and leaf senescence, implying a large spectrum of functions for the SCF pathway in plant development. Here, we present a molecular and functional characterization of plant cullins. TheArabidopsis genome contains 11 cullin-related genes. Complementation assays revealed that AtCUL1 but not AtCUL4 can functionally complement the yeast cdc53 mutant.Arabidopsis mutants containing transfer DNA (T-DNA) insertions in the AtCUL1 gene were shown to display an arrest in early embryogenesis. Consistently, both the transcript and the protein of the AtCUL1 gene were found to accumulate in embryos. The AtCUL1 protein localized mainly in the nucleus but also weakly in the cytoplasm during interphase and colocalized with the mitotic spindle in metaphase. Our results demonstrate a critical role for the SCF ubiquitin ligase inArabidopsis embryogenesis.

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49

Kim, Y. J., L. Francisco, G. C. Chen, E. Marcotte y C. S. Chan. "Control of cellular morphogenesis by the Ip12/Bem2 GTPase-activating protein: possible role of protein phosphorylation." Journal of Cell Biology 127, n.º 5 (1 de diciembre de 1994): 1381–94. http://dx.doi.org/10.1083/jcb.127.5.1381.

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The IPL2 gene is known to be required for normal polarized cell growth in the budding yeast Saccharomyces cerevisiae. We now show that IPL2 is identical to the previously identified BEM2 gene. bem2 mutants are defective in bud site selection at 26 degrees C and localized cell surface growth and organization of the actin cytoskeleton at 37 degrees C. BEM2 encodes a protein with a COOH-terminal domain homologous to sequences found in several GTPase-activating proteins, including human Bcr. The GTPase-activating protein-domain from the Bem2 protein (Bem2p) or human Bcr can functionally substitute for Bem2p. The Rho1 and Rho2 GTPases are the likely in vivo targets of Bem2p because bem2 mutant phenotypes can be partially suppressed by increasing the gene dosage of RHO1 or RHO2. CDC55 encodes the putative regulatory B subunit of protein phosphatase 2A, and mutations in BEM2 have previously been identified as suppressors of the cdc55-1 mutation. We show here that mutations in the previously identified GRR1 gene can suppress bem2 mutations. grr1 and cdc55 mutants are both elongated in shape and cold-sensitive for growth, and cells lacking both GRR1 and CDC55 exhibit a synthetic lethal phenotype. bem2 mutant phenotypes also can be suppressed by the SSD1-vl (also known as SRK1) mutation, which was shown previously to suppress mutations in the protein phosphatase-encoding SIT4 gene. Cells lacking both BEM2 and SIT4 exhibit a synthetic lethal phenotype even in the presence of the SSD1-v1 suppressor. These genetic interactions together suggest that protein phosphorylation and dephosphorylation play an important role in the BEM2-mediated process of polarized cell growth.

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50

Ben-Yehuda, Sigal, Caroline S. Russell, Ian Dix, Jean D. Beggs y Martin Kupiec. "Extensive Genetic Interactions Between PRP8 and PRP17/CDC40, Two Yeast Genes Involved in Pre-mRNA Splicing and Cell Cycle Progression". Genetics 154, n.º 1 (1 de enero de 2000): 61–71. http://dx.doi.org/10.1093/genetics/154.1.61.

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Abstract Biochemical and genetic experiments have shown that the PRP17 gene of the yeast Saccharomyces cerevisiae encodes a protein that plays a role during the second catalytic step of the splicing reaction. It was found recently that PRP17 is identical to the cell division cycle CDC40 gene. cdc40 mutants arrest at the restrictive temperature after the completion of DNA replication. Although the PRP17/CDC40 gene product is essential only at elevated temperatures, splicing intermediates accumulate in prp17 mutants even at the permissive temperature. In this report we describe extensive genetic interactions between PRP17/CDC40 and the PRP8 gene. PRP8 encodes a highly conserved U5 snRNP protein required for spliceosome assembly and for both catalytic steps of the splicing reaction. We show that mutations in the PRP8 gene are able to suppress the temperature-sensitive growth phenotype and the splicing defect conferred by the absence of the Prp17 protein. In addition, these mutations are capable of suppressing certain alterations in the conserved PyAG trinucleotide at the 3′ splice junction, as detected by an ACT1-CUP1 splicing reporter system. Moreover, other PRP8 alleles exhibit synthetic lethality with the absence of Prp17p and show a reduced ability to splice an intron bearing an altered 3′ splice junction. On the basis of these findings, we propose a model for the mode of interaction between the Prp8 and Prp17 proteins during the second catalytic step of the splicing reaction.

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