Articoli di riviste: "HMG-box proteins"

1

Bianchi, Marco E., e Monica Beltrame. "Flexing DNA: HMG-Box Proteins and Their Partners". American Journal of Human Genetics 63, n. 6 (dicembre 1998): 1573–77. http://dx.doi.org/10.1086/302170.

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2

Xin, H. "DNA binding by single HMG box model proteins". Nucleic Acids Research 28, n. 20 (15 ottobre 2000): 4044–50. http://dx.doi.org/10.1093/nar/28.20.4044.

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3

Schulman, I. G., T. Wang, M. Wu, J. Bowen, R. G. Cook, M. A. Gorovsky e C. D. Allis. "Macronuclei and micronuclei in Tetrahymena thermophila contain high-mobility-group-like chromosomal proteins containing a highly conserved eleven-amino-acid putative DNA-binding sequence." Molecular and Cellular Biology 11, n. 1 (gennaio 1991): 166–74. http://dx.doi.org/10.1128/mcb.11.1.166.

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HMG (high-mobility-group protein) B and HMG C are abundant nonhistone chromosomal proteins isolated from Tetrahymena thermophila macronuclei with solubilities, molecular weights, and amino acid compositions like those of vertebrate HMG proteins. Genomic clones encoding each of these proteins have been sequenced. Both are single-copy genes that encode single polyadenylated messages whose amounts are 10 to 15 times greater in growing cells than in starved, nongrowing cells. The derived amino acid sequences of HMG B and HMG C contain a highly conserved sequence, the HMG 1 box, found in vertebrate HMGs 1 and 2, and we speculate that this sequence may represent a novel, previously unrecognized DNA-binding motif in this class of chromosomal proteins. Like HMGs 1 and 2, HMGs B and C contain a high percentage of aromatic amino acids. However, the Tetrahymena HMGs are small, are associated with nucleosome core particles, and can be specifically extracted from macronuclei by elutive intercalation, properties associated with vertebrate HMGs 14 and 17, not HMGs 1 and 2. Thus, it appears that these Tetrahymena proteins have features in common with both of the major subgroups of higher eucaryotic HMG proteins. Surprisingly, a linker histone found exclusively in transcriptionally inactive micronuclei also has several HMG-like characteristics, including the ability to be specifically extracted from nuclei by elutive intercalation and the presence of the HMG 1 box. This finding suggests that at least in T. thermophila, proteins with HMG-like properties are not restricted to regions of transcriptionally active chromatin.

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4

Schulman, I. G., T. Wang, M. Wu, J. Bowen, R. G. Cook, M. A. Gorovsky e C. D. Allis. "Macronuclei and micronuclei in Tetrahymena thermophila contain high-mobility-group-like chromosomal proteins containing a highly conserved eleven-amino-acid putative DNA-binding sequence". Molecular and Cellular Biology 11, n. 1 (gennaio 1991): 166–74. http://dx.doi.org/10.1128/mcb.11.1.166-174.1991.

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HMG (high-mobility-group protein) B and HMG C are abundant nonhistone chromosomal proteins isolated from Tetrahymena thermophila macronuclei with solubilities, molecular weights, and amino acid compositions like those of vertebrate HMG proteins. Genomic clones encoding each of these proteins have been sequenced. Both are single-copy genes that encode single polyadenylated messages whose amounts are 10 to 15 times greater in growing cells than in starved, nongrowing cells. The derived amino acid sequences of HMG B and HMG C contain a highly conserved sequence, the HMG 1 box, found in vertebrate HMGs 1 and 2, and we speculate that this sequence may represent a novel, previously unrecognized DNA-binding motif in this class of chromosomal proteins. Like HMGs 1 and 2, HMGs B and C contain a high percentage of aromatic amino acids. However, the Tetrahymena HMGs are small, are associated with nucleosome core particles, and can be specifically extracted from macronuclei by elutive intercalation, properties associated with vertebrate HMGs 14 and 17, not HMGs 1 and 2. Thus, it appears that these Tetrahymena proteins have features in common with both of the major subgroups of higher eucaryotic HMG proteins. Surprisingly, a linker histone found exclusively in transcriptionally inactive micronuclei also has several HMG-like characteristics, including the ability to be specifically extracted from nuclei by elutive intercalation and the presence of the HMG 1 box. This finding suggests that at least in T. thermophila, proteins with HMG-like properties are not restricted to regions of transcriptionally active chromatin.

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5

Veilleux, Stéphane, e Guylain Boissonneault. "Dynamics of Reporter Gene Stimulation by HMG Box Proteins". DNA and Cell Biology 21, n. 3 (marzo 2002): 199–212. http://dx.doi.org/10.1089/10445490252925440.

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6

Briquet, Sylvie, Charlotte Boschet, Mathieu Gissot, Emilie Tissandié, Elisa Sevilla, Jean-François Franetich, Isabelle Thiery, Zuhal Hamid, Catherine Bourgouin e Catherine Vaquero. "High-Mobility-Group Box Nuclear Factors of Plasmodium falciparum". Eukaryotic Cell 5, n. 4 (aprile 2006): 672–82. http://dx.doi.org/10.1128/ec.5.4.672-682.2006.

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ABSTRACT In eukaryotes, the high-mobility-group (HMG) nuclear factors are highly conserved throughout evolution and are divided into three families, including HGMB, characterized by an HMG box domain. Some HMGB factors are DNA structure specific and preferentially interact with distorted DNA sequences, trigger DNA bending, and hence facilitate the binding of nucleoprotein complexes that in turn activate or repress transcription. In Plasmodium falciparum, two HMGB factors were predicted: PfHMGB1 and PfHMGB2. They are small proteins, under 100 amino acids long, encompassing a characteristic HMG box domain closely related to box B of metazoan factors, which comprises two HMG box domains, A and B, in tandem. Computational analyses supported the conclusion that the Plasmodium proteins were genuine architectural HMGB factors, and in vitro analyses performed with both recombinant proteins established that they were able to interact with distorted DNA structures and bend linear DNA with different affinities. These proteins were detected in both asexual- and gametocyte-stage cells in Western blotting experiments and mainly in the parasite nuclei. PfHMGB1 is preferentially expressed in asexual erythrocytic stages and PfHMGB2 in gametocytes, in good correlation with transcript levels of expression. Finally, immunofluorescence studies revealed differential subcellular localizations: both factors were observed in the nucleus of asexual- and sexual-stage cells, and PfHMGB2 was also detected in the cytoplasm of gametocytes. In conclusion, in light of differences in their levels of expression, subcellular localizations, and capacities for binding and bending DNA, these factors are likely to play nonredundant roles in transcriptional regulation of Plasmodium development in erythrocytes.

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7

Kalinowska-Herok, Magdalena, e Piotr Widłak. "High mobility group proteins stimulate DNA cleavage by apoptotic endonuclease DFF40/CAD due to HMG-box interactions with DNA." Acta Biochimica Polonica 55, n. 1 (1 febbraio 2008): 21–26. http://dx.doi.org/10.18388/abp.2008_3196.

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The DFF40/CAD endonuclease is primarily responsible for internucleosomal DNA cleavage during the terminal stages of apoptosis. It has been previously demonstrated that the major HMG-box-containing chromatin proteins HMGB1 and HMGB2 stimulate naked DNA cleavage by DFF40/CAD. Here we investigate the mechanism of this stimulation and show that HMGB1 neither binds to DFF40/CAD nor enhances its ability for stable binding to DNA. Comparison of the stimulatory activities of different truncated forms of HMGB1 protein indicates that a structural array of two HMG-boxes is required for such stimulation. HMG-boxes are known to confer specific local distortions of DNA structure upon binding. Interestingly, the presence of DNA strand cross-links formed by cisplatin or transplatin, which may somehow mimic distortions induced by HMG-boxes, also affects DNA cleavage by the nuclease. The data presented suggest that changes induced in DNA conformation upon HMG-box binding makes the substrate more accessible to cleavage by DFF40/CAD nuclease and thus may contribute to preferential linker DNA cleavage during apoptosis.

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8

Landsman, David, e Michael Bustin. "A signature for the HMG-1 box DNA-binding proteins". BioEssays 15, n. 8 (agosto 1993): 539–46. http://dx.doi.org/10.1002/bies.950150807.

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9

Takusagawa, Mari, Yusuke Kobayashi, Yoichiro Fukao, Kumi Hidaka, Masayuki Endo, Hiroshi Sugiyama, Takashi Hamaji et al. "HBD1 protein with a tandem repeat of two HMG-box domains is a DNA clip to organize chloroplast nucleoids in Chlamydomonas reinhardtii". Proceedings of the National Academy of Sciences 118, n. 20 (11 maggio 2021): e2021053118. http://dx.doi.org/10.1073/pnas.2021053118.

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Compaction of bulky DNA is a universal issue for all DNA-based life forms. Chloroplast nucleoids (chloroplast DNA–protein complexes) are critical for chloroplast DNA maintenance and transcription, thereby supporting photosynthesis, but their detailed structure remains enigmatic. Our proteomic analysis of chloroplast nucleoids of the green alga Chlamydomonas reinhardtii identified a protein (HBD1) with a tandem repeat of two DNA-binding high mobility group box (HMG-box) domains, which is structurally similar to major mitochondrial nucleoid proteins transcription factor A, mitochondrial (TFAM), and ARS binding factor 2 protein (Abf2p). Disruption of the HBD1 gene by CRISPR-Cas9–mediated genome editing resulted in the scattering of chloroplast nucleoids. This phenotype was complemented when intact HBD1 was reintroduced, whereas a truncated HBD1 with a single HMG-box domain failed to complement the phenotype. Furthermore, ectopic expression of HBD1 in the mitochondria of yeast Δabf2 mutant successfully complemented the defects, suggesting functional similarity between HBD1 and Abf2p. Furthermore, in vitro assays of HBD1, including the electrophoretic mobility shift assay and DNA origami/atomic force microscopy, showed that HBD1 is capable of introducing U-turns and cross-strand bridges, indicating that proteins with two HMG-box domains would function as DNA clips to compact DNA in both chloroplast and mitochondrial nucleoids.

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10

de Froidmont, D., C. Lejour, P. Stoeva e J. M. Jacquemin. "Endosperm Box Binding Proteins: cDNA Cloning of a Wheat HMG Protein". Biotechnology & Biotechnological Equipment 10, n. 1 (gennaio 1996): 15–26. http://dx.doi.org/10.1080/13102818.1996.10818875.

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11

Chow, Christine S., e Stephen J. Lippard. "Recognition of cisplatin-modified DNA by proteins with HMG-box domains". Journal of Inorganic Biochemistry 51, n. 1-2 (luglio 1993): 392. http://dx.doi.org/10.1016/0162-0134(93)85421-4.

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12

Visacka, Katarina, Joachim M. Gerhold, Jana Petrovicova, Slavomir Kinsky, Priit Jõers, Jozef Nosek, Juhan Sedman e Lubomir Tomaska. "Novel subfamily of mitochondrial HMG box-containing proteins: functional analysis of Gcf1p from Candida albicans". Microbiology 155, n. 4 (1 aprile 2009): 1226–40. http://dx.doi.org/10.1099/mic.0.025759-0.

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Mitochondria of eukaryotic organisms contain populations of DNA molecules that are packed into higher-order structures called mitochondrial nucleoids (mt-nucleoids). In Saccharomyces cerevisiae, the compaction of mitochondrial DNA (mtDNA) into mt-nucleoids is mediated primarily by the high-mobility group (HMG) box-containing protein Abf2, which is an important player in stabilization and metabolism of mtDNA. Although it is evident that analogous proteins must exist in other yeast species, an apparently fast divergence rate has precluded their identification, characterization and comparative analysis. Using in silico analysis of the complete genome sequence of the pathogenic yeast Candida albicans we predicted that the ORF 19.400/19.8030 assigned as GCF1 encodes a putative mitochondrial HMG box-containing protein. In contrast to Abf2p, which contains two HMG boxes, Gcf1p contains only one C-terminal HMG box. In addition, it contains one putative coiled-coil domain with a potential role in protein dimerization. Fluorescence microscopy analysis of a C-terminally tagged Gcf1p with green fluorescent protein (GFP) revealed its mitochondrial localization in both heterologous (S. cerevisiae) and native (C. albicans) hosts. Biochemical analyses of DNA-binding properties indicate that Gcf1p is, similarly to Abf2p, a non-specific DNA-binding protein. To analyse the role of Gcf1p in mtDNA metabolism, we constructed strains lacking one functional allele of the GCF1 gene and carrying one GCF1 allele under the control of the MET3 promoter. Under repressible conditions this strain exhibited a more than 3000-fold decrease in levels of GCF1 mRNA, which was correlated with a substantial decrease in the number of mtDNA copies as well as recombination intermediates. The dramatic effect of reduced levels of Gcf1p on mtDNA metabolism indicates that the protein is involved in essential molecular transactions that relate to the mitochondrial genome.

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13

Pallier, Coralie, Paola Scaffidi, Stéphanie Chopineau-Proust, Alessandra Agresti, Patrice Nordmann, Marco E. Bianchi e Vincent Marechal. "Association of Chromatin Proteins High Mobility Group Box (HMGB) 1 and HMGB2 with Mitotic Chromosomes". Molecular Biology of the Cell 14, n. 8 (agosto 2003): 3414–26. http://dx.doi.org/10.1091/mbc.e02-09-0581.

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High mobility group box (HMGB) 1 and 2 are two abundant nonhistone nuclear proteins that have been found in association with chromatin. Previous studies based on immunofluorescence analysis indicated that HMGB1 dissociates from chromosomes during mitosis. In the present work, HMGB1 and 2 subcellular localization was reinvestigated in living cells by using enhanced green fluorescent protein- and Discosome sp. red fluorescent protein-tagged proteins. Contrary to previous reports, HMGB1 and 2 were shown to be present under two forms in mitotic cells, i.e., free and associated with the condensed chromatin, which rapidly exchange. A detailed analysis of HMGB2 interaction with mitotic chromosomes indicated that two sites encompassing HMG-box A and B are responsible for binding. Importantly, this interaction was rapidly inactivated when cells were permeabilized or exposed to chemical fixatives that are widely used in immunodetection techniques. A comparable behavior was also observed for two proteins of the HMG-nucleosome binding (HMGN) group, namely, HMGN1 and HMGN2.

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14

Poulat, F., F. Girard, M. P. Chevron, C. Gozé, X. Rebillard, B. Calas, N. Lamb e P. Berta. "Nuclear localization of the testis determining gene product SRY." Journal of Cell Biology 128, n. 5 (1 marzo 1995): 737–48. http://dx.doi.org/10.1083/jcb.128.5.737.

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We have studied the expression of the human SRY protein (termed p27SRY) in two different cell lines by using specific antibodies. Confocal microscopy enabled us to localize p27SRY precisely in the nucleus in a discrete punctuate pattern. Furthermore, through microinjection experiments, we have demonstrated that the localization of the p27SRY protein into the nucleus was an event involving the NH2-terminal part of the high mobility group (HMG) domain. With the help of several synthetic peptides and various p27SRY mutants, we have characterized a bipartite basic motif in this part of the protein corresponding to a nuclear localization signal. This nuclear localization signal appears to be highly conserved in SRY box- and HMB box-containing proteins, suggesting common properties of nuclear targeting within the HMG box protein family.

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15

Lichota, J., e K. D. Grasser. "Interaction of Maize Chromatin-Associated HMG Proteins with Mononucleosomes: Role of Core and Linker Histones". Biological Chemistry 384, n. 7 (15 luglio 2003): 1019–27. http://dx.doi.org/10.1515/bc.2003.114.

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AbstractTwo groups of plant chromatin-associated high mobility group (HMG) proteins, namely the HMGA family, typically containing four A/T-hook DNA-binding motifs, and the HMGB family, containing a single HMG-box DNA-binding domain, have been identified. We have examined the interaction of recombinant maize HMGA and five different HMGB proteins with mononucleosomes (containing approx. 165 bp of DNA) purified from micrococcal nuclease-digested maize chromatin. The HMGB proteins interacted with the nucleosomes independent of the presence of the linker histone H1, while the binding of HMGA in the presence of H1 differed from that observed in the absence of H1. HMGA and the HMGB proteins bound H1-containing nucleosome particles with similar affinity. The plant HMG proteins could also bind nucleosomes that were briefly treated with trypsin (removing the N-terminal domains of the core histones), suggesting that the histone N-termini are dispensable for HMG protein binding. In the presence of untreated nucleosomes and trypsinised nucleosomes, HMGB1 could be chemically crosslinked with a core histone, which indicates that the trypsin-resistant part of the histones within the nucleosome is the main interaction partner of HMGB1 rather than the histone N-termini. In conclusion, these results indicate that specific nucleosome binding of the plant HMGB proteins requires simultaneous DNA and histone contacts.

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16

Thomas, J. O. "HMG1 and 2: architectural DNA-binding proteins". Biochemical Society Transactions 29, n. 4 (1 agosto 2001): 395–401. http://dx.doi.org/10.1042/bst0290395.

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HMG1 and 2 (high mobility group proteins 1 and 2; renamed HMGB1 and 2) contain two DNA-binding HMG-box domains (A and B) and a long acidic C-terminal domain. They bind DNA without sequence specificity, but have a high affinity for bent or distorted DNA, and bend linear DNA. The individual A and B boxes (which, although broadly similar, show both structural and functional differences) exhibit many of the structure-specific properties of the whole protein. The acidic tail modulates the affinity of the tandem HMG boxes in HMG1 and 2 for a variety of DNA targets, including four-way junctions, but not distorted DNA minicircles, to which the proteins bind with very high affinity. HMG1 and 2 appear to play important architectural roles in the assembly of nucleoprotein complexes in a variety of biological processes, for example V(D)J recombination, the initiation of transcription, and DNA repair.

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Yamaguchi-Shinozaki, Kazuko, e Kazuo Shinozaki. "A novelArabidopsisDNA binding protein contains the conserved motif of HMG-box proteins". Nucleic Acids Research 20, n. 24 (1992): 6737. http://dx.doi.org/10.1093/nar/20.24.6737.

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18

Guldner, H. H., C. Szostecki, P. Schroder, U. Matschl, K. Jensen, C. Luders, H. Will e T. Sternsdorf. "Splice variants of the nuclear dot-associated Sp100 protein contain homologies to HMG-1 and a human nuclear phosphoprotein-box motif". Journal of Cell Science 112, n. 5 (1 marzo 1999): 733–47. http://dx.doi.org/10.1242/jcs.112.5.733.

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Sp100 and PML are interferon-inducible proteins associated with a new class of nuclear domains (known as nuclear dots or PML bodies) which play a role in tumorigenesis, virus infections, and autoimmunity. While PML is extensively alternatively spliced, only two splice variants are known for Sp100. Here we describe the identification and characterization of several Sp100 splice variant proteins and support their existence by elucidation of the 3′-end of the Sp100 gene. Some of the splice variants contain a domain of significant sequence similarity with two previously described highly related interferon-inducible nuclear phosphoproteins as well as to suppressin and DEAF-1, which altogether define a novel protein motif, termed HNPP-box. One class of splice variants contains an almost complete and highly conserved copy of the DNA-binding high mobility group 1 protein sequence and thus represent novel HMG-box proteins. When expressed transiently, both major classes of Sp100 splice variant proteins localize in part to nuclear dots/PML bodies and in addition to different nuclear domains. Furthermore, PML was occasionally redistributed. These data indicate that alternatively spliced Sp100 proteins are expressed, differ in part in localization from Sp100, and might bind to chromatin via the HMG domain.

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Vozáriková, Veronika, Nina Kunová, Jacob A. Bauer, Ján Frankovský, Veronika Kotrasová, Katarína Procházková, Vladimíra Džugasová et al. "Mitochondrial HMG-Box Containing Proteins: From Biochemical Properties to the Roles in Human Diseases". Biomolecules 10, n. 8 (16 agosto 2020): 1193. http://dx.doi.org/10.3390/biom10081193.

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Mitochondrial DNA (mtDNA) molecules are packaged into compact nucleo-protein structures called mitochondrial nucleoids (mt-nucleoids). Their compaction is mediated in part by high-mobility group (HMG)-box containing proteins (mtHMG proteins), whose additional roles include the protection of mtDNA against damage, the regulation of gene expression and the segregation of mtDNA into daughter organelles. The molecular mechanisms underlying these functions have been identified through extensive biochemical, genetic, and structural studies, particularly on yeast (Abf2) and mammalian mitochondrial transcription factor A (TFAM) mtHMG proteins. The aim of this paper is to provide a comprehensive overview of the biochemical properties of mtHMG proteins, the structural basis of their interaction with DNA, their roles in various mtDNA transactions, and the evolutionary trajectories leading to their rapid diversification. We also describe how defects in the maintenance of mtDNA in cells with dysfunctional mtHMG proteins lead to different pathologies at the cellular and organismal level.

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20

Swanson, Patrick C. "A RAG-1/RAG-2 Tetramer Supports 12/23-Regulated Synapsis, Cleavage, and Transposition of V(D)J Recombination Signals". Molecular and Cellular Biology 22, n. 22 (15 novembre 2002): 7790–801. http://dx.doi.org/10.1128/mcb.22.22.7790-7801.2002.

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ABSTRACT Initiation of V(D)J recombination involves the synapsis and cleavage of a 12/23 pair of recombination signal sequences by RAG-1 and RAG-2. Ubiquitous nonspecific DNA-bending factors of the HMG box family, such as HMG-1, are known to assist in these processes. After cleavage, the RAG proteins remain bound to the cut signal ends and, at least in vitro, support the integration of these ends into unrelated target DNA via a transposition-like mechanism. To investigate whether the protein complex supporting synapsis, cleavage, and transposition of V(D)J recombination signals utilized the same complement of RAG and HMG proteins, I compared the RAG protein stoichiometries and activities of discrete protein-DNA complexes assembled on intact, prenicked, or precleaved recombination signal sequence (RSS) substrates in the absence and presence of HMG-1. In the absence of HMG-1, I found that two discrete RAG-1/RAG-2 complexes are detected by mobility shift assay on all RSS substrates tested. Both contain dimeric RAG-1 and either one or two RAG-2 subunits. The addition of HMG-1 supershifts both complexes without altering the RAG protein stoichiometry. I find that 12/23-regulated recombination signal synapsis and cleavage are only supported in a protein-DNA complex containing HMG-1 and a RAG-1/RAG-2 tetramer. Interestingly, the RAG-1/RAG-2 tetramer also supports transposition, but HMG-1 is dispensable for its activity.

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Oñate, S. A., P. Prendergast, J. P. Wagner, M. Nissen, R. Reeves, D. E. Pettijohn e D. P. Edwards. "The DNA-bending protein HMG-1 enhances progesterone receptor binding to its target DNA sequences." Molecular and Cellular Biology 14, n. 5 (maggio 1994): 3376–91. http://dx.doi.org/10.1128/mcb.14.5.3376.

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Steroid hormone receptors are ligand-dependent transcriptional activators that exert their effects by binding as dimers to cis-acting DNA sequences termed hormone response elements. When human progesterone receptor (PR), expressed as a full-length protein in a baculovirus system, was purified to homogeneity, it retained its ability to bind hormonal ligand and to dimerize but exhibited a dramatic loss in DNA binding activity for specific progesterone response elements (PREs). Addition of nuclear extracts from several cellular sources restored DNA binding activity, suggesting that PR requires a ubiquitous accessory protein for efficient interaction with specific DNA sequences. Here we have demonstrated that the high-mobility-group chromatin protein HMG-1, as a highly purified protein, dramatically enhanced binding of purified PR to PREs in gel mobility shift assays. This effect appeared to be highly selective for HMG-1, since a number of other nonspecific proteins failed to enhance PRE binding. Moreover, HMG-1 was effective when added in stoichiometric amounts with receptor, and it was capable of enhancing the DNA binding of both the A and B amino-terminal variants of PR. The presence of HMG-1 measurably increased the binding affinity of purified PR by 10-fold when a synthetic palindromic PRE was the target DNA. The increase in binding affinity for a partial palindromic PRE present in natural target genes was greater than 10-fold. Coimmunoprecipitation assays using anti-PR or anti-HMG-1 antibodies demonstrated that both PR and HMG-1 are present in the enhanced complex with PRE. HMG-1 protein has two conserved DNA binding domains (A and B), which recognize DNA structure rather than specific sequences. The A- or B-box domain expressed and purified from Escherichia coli independently stimulated the binding of PR to PRE, and the B box was able to functionally substitute for HMG-1 in enhancing PR binding. DNA ligase-mediated ring closure assays demonstrated that both the A and B binding domains mediate DNA flexure. It was also demonstrated in competition binding studies that the intact HMG-1 protein binds to tightly curved covalently closed or relaxed DNA sequences in preference to the same sequence in linear form. The finding that enhanced PRE binding was intrinsic to the HMG-1 box, combined with the demonstration that HMG-1 or its DNA binding boxes can flex DNA, suggests that HMG-1 facilitates the binding of PR by inducing a structural change in the target DNA.

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Oñate, S. A., P. Prendergast, J. P. Wagner, M. Nissen, R. Reeves, D. E. Pettijohn e D. P. Edwards. "The DNA-bending protein HMG-1 enhances progesterone receptor binding to its target DNA sequences". Molecular and Cellular Biology 14, n. 5 (maggio 1994): 3376–91. http://dx.doi.org/10.1128/mcb.14.5.3376-3391.1994.

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Abstract (sommario):

Steroid hormone receptors are ligand-dependent transcriptional activators that exert their effects by binding as dimers to cis-acting DNA sequences termed hormone response elements. When human progesterone receptor (PR), expressed as a full-length protein in a baculovirus system, was purified to homogeneity, it retained its ability to bind hormonal ligand and to dimerize but exhibited a dramatic loss in DNA binding activity for specific progesterone response elements (PREs). Addition of nuclear extracts from several cellular sources restored DNA binding activity, suggesting that PR requires a ubiquitous accessory protein for efficient interaction with specific DNA sequences. Here we have demonstrated that the high-mobility-group chromatin protein HMG-1, as a highly purified protein, dramatically enhanced binding of purified PR to PREs in gel mobility shift assays. This effect appeared to be highly selective for HMG-1, since a number of other nonspecific proteins failed to enhance PRE binding. Moreover, HMG-1 was effective when added in stoichiometric amounts with receptor, and it was capable of enhancing the DNA binding of both the A and B amino-terminal variants of PR. The presence of HMG-1 measurably increased the binding affinity of purified PR by 10-fold when a synthetic palindromic PRE was the target DNA. The increase in binding affinity for a partial palindromic PRE present in natural target genes was greater than 10-fold. Coimmunoprecipitation assays using anti-PR or anti-HMG-1 antibodies demonstrated that both PR and HMG-1 are present in the enhanced complex with PRE. HMG-1 protein has two conserved DNA binding domains (A and B), which recognize DNA structure rather than specific sequences. The A- or B-box domain expressed and purified from Escherichia coli independently stimulated the binding of PR to PRE, and the B box was able to functionally substitute for HMG-1 in enhancing PR binding. DNA ligase-mediated ring closure assays demonstrated that both the A and B binding domains mediate DNA flexure. It was also demonstrated in competition binding studies that the intact HMG-1 protein binds to tightly curved covalently closed or relaxed DNA sequences in preference to the same sequence in linear form. The finding that enhanced PRE binding was intrinsic to the HMG-1 box, combined with the demonstration that HMG-1 or its DNA binding boxes can flex DNA, suggests that HMG-1 facilitates the binding of PR by inducing a structural change in the target DNA.

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PÖHLER, J. RICHARD G., e DAVID M. J. LILLEY. "186 The interaction of HMG-box proteins with the four-way DNA junction". Biochemical Society Transactions 25, n. 4 (1 novembre 1997): S647. http://dx.doi.org/10.1042/bst025s647.

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24

Zhao, Yufen, Wenjie Cheng, Corinne L. D. Gibb, Goutam Gupta e Neville R. Kallenbach. "HMG Box Proteins Interact With Multiple Tandemly Repeated (GCC)n•(GGC)mDNA Sequences". Journal of Biomolecular Structure and Dynamics 14, n. 2 (ottobre 1996): 235–38. http://dx.doi.org/10.1080/07391102.1996.10508113.

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25

Pohler, J. R. G. "HMG box proteins bind to four-way DNA junctions in their open conformation". EMBO Journal 17, n. 3 (1 febbraio 1998): 817–26. http://dx.doi.org/10.1093/emboj/17.3.817.

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26

Ellwood, Katharine B., Yi-Meng Yen, Reid C. Johnson e Michael Carey. "Mechanism for Specificity by HMG-1 in Enhanceosome Assembly". Molecular and Cellular Biology 20, n. 12 (15 giugno 2000): 4359–70. http://dx.doi.org/10.1128/mcb.20.12.4359-4370.2000.

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ABSTRACT Assembly of enhanceosomes requires architectural proteins to facilitate the DNA conformational changes accompanying cooperative binding of activators to a regulatory sequence. The architectural protein HMG-1 has been proposed to bind DNA in a sequence-independent manner, yet, paradoxically, it facilitates specific DNA binding reactions in vitro. To investigate the mechanism of specificity we explored the effect of HMG-1 on binding of the Epstein-Barr virus activator ZEBRA to a natural responsive promoter in vitro. DNase I footprinting, mutagenesis, and electrophoretic mobility shift assay reveal that HMG-1 binds cooperatively with ZEBRA to a specific DNA sequence between two adjacent ZEBRA recognition sites. This binding requires a strict alignment between two adjacent ZEBRA sites and both HMG boxes of HMG-1. Our study provides the first demonstration of sequence-dependent binding by a nonspecific HMG-box protein. We hypothesize how a ubiquitous, nonspecific architectural protein can function in a specific context through the use of rudimentary sequence recognition coupled with cooperativity. The observation that an abundant architectural protein can bind DNA cooperatively and specifically has implications towards understanding HMG-1's role in mediating DNA transactions in a variety of enzymological systems.

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27

Brewster, Neil K., Gerald C. Johnston e Richard A. Singer. "A Bipartite Yeast SSRP1 Analog Comprised of Pob3 and Nhp6 Proteins Modulates Transcription". Molecular and Cellular Biology 21, n. 10 (15 maggio 2001): 3491–502. http://dx.doi.org/10.1128/mcb.21.10.3491-3502.2001.

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ABSTRACT The FACT complex of vertebrate cells, comprising the Cdc68 (Spt16) and SSRP1 proteins, facilitates transcription elongation on a nucleosomal template and modulates the elongation-inhibitory effects of the DSIF complex in vitro. Genetic findings show that the related yeast (Saccharomyces cerevisiae) complex, termed CP, also mediates transcription. The CP components Cdc68 and Pob3 closely resemble the FACT components, except that the C-terminal high-mobility group (HMG) box domain of SSRP1 is not found in the yeast homolog Pob3. We show here that Nhp6a and Nhp6b, small HMG box proteins with overlapping functions in yeast, associate with the CP complex and mediate CP-related genetic effects on transcription. Absence of the Nhp6 proteins causes severe impairment in combination with mutations impairing the Swi-Snf chromatin-remodeling complex and the DSIF (Spt4 plus Spt5) elongation regulator, and sensitizes cells to 6-azauracil, characteristic of elongation effects. An artificial SSRP1-like protein, created by fusing the Pob3 and Nhp6a proteins, provides both Pob3 and Nhp6a functions for transcription, and competition experiments indicate that these functions are exerted in association with Cdc68. This particular Pob3-Nhp6a fusion protein was limited for certain Nhp6 activities, indicating that its Nhp6a function is compromised. These findings suggest that in yeast cells the Cdc68 partners may be both Pob3 and Nhp6, functioning as a bipartite analog of the vertebrate SSRP1 protein.

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28

Oliver, Antony W., Sarah A. Jones, Stephen Mark Roe, Steve Matthews, Graham H. Goodwin e Laurence H. Pearl. "Crystal structure of the proximal BAH domain of the polybromo protein". Biochemical Journal 389, n. 3 (26 luglio 2005): 657–64. http://dx.doi.org/10.1042/bj20050310.

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The BAH domain (bromo-associated homology domain) was first identified from a repeated motif found in the nuclear protein polybromo – a large (187 kDa) modular protein comprising six bromodomains, two BAH domains and an HMG box. To date, the BAH domain has no ascribed function, although it is found in a wide range of proteins that contain additional domains involved in either transcriptional regulation (e.g. SET, PHD and bromodomain) and/or DNA binding (HMG box and AT hook). The molecular function of polybromo itself also remains unclear, but it has been identified as a key component of an SWI/SNF (switching/sucrose non-fermenting)-related, ATP-dependent chromatin-remodelling complex PBAF (polybromo, BRG1-associated factors; also known as SWI/SNF-B or SWI/SNFβ). We present in this paper the crystal structure of the proximal BAH domain from chicken polybromo (BAH1), at a resolution of 1.6 Å (1 Å=0.1 nm). Structure-based sequence analysis reveals several features that may be involved in mediating protein–protein interactions.

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29

Wang, T., e C. D. Allis. "An abundant high-mobility-group-like protein is targeted to micronuclei in a cell cycle-dependent and developmentally regulated fashion in Tetrahymena thermophila." Molecular and Cellular Biology 13, n. 1 (gennaio 1993): 163–73. http://dx.doi.org/10.1128/mcb.13.1.163.

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In this report, we have demonstrated for the first time that an abundant high-mobility-group (HMG)-like protein, HMG B, previously thought to be specific to macronuclei in Tetrahymena thermophila, is also present in micronuclei. Biochemical data document the fact that HMG B is extremely labile in micronuclei. Unless extreme precautions are taken during the isolation of nuclei (addition of 1% formaldehyde to the nucleus isolation buffer), HMG B is not detected in micronuclei. Using polyclonal antibodies highly selective for HMG B, immunoblotting and immunofluorescence analyses show that the presence of HMG B in micronuclei is dynamic, correlating well with known periods of micronuclear DNA replication. This is the case not only during the vegetative cell cycle but also during early stages of the sexual cycle, conjugation, when the presence of HMG B in micronuclei is also closely correlated with meiotic DNA recombination and repair. Since micronuclei are transcriptionally inactive during vegetative growth, our data lend support to the idea that HMG B does not function exclusively in the establishment of transcriptionally competent chromatin. However, micronuclei are transcriptionally active during early stages of conjugation. Evidence that HMG B is strongly synthesized and deposited into micronuclei during this stage is presented. Therefore, it is tempting to suggest that HMG B may play an important role in remodeling micronuclear chromatin into an "active," more open configuration. We favor a model wherein HMG B, like other abundant, low-specificity HMG box-containing proteins, functions to wrap DNA, presumably modulating higher-order chromatin structure for a broad range of biological processes, including transcription and replication.

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30

Wang, T., e C. D. Allis. "An abundant high-mobility-group-like protein is targeted to micronuclei in a cell cycle-dependent and developmentally regulated fashion in Tetrahymena thermophila". Molecular and Cellular Biology 13, n. 1 (gennaio 1993): 163–73. http://dx.doi.org/10.1128/mcb.13.1.163-173.1993.

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Abstract (sommario):

In this report, we have demonstrated for the first time that an abundant high-mobility-group (HMG)-like protein, HMG B, previously thought to be specific to macronuclei in Tetrahymena thermophila, is also present in micronuclei. Biochemical data document the fact that HMG B is extremely labile in micronuclei. Unless extreme precautions are taken during the isolation of nuclei (addition of 1% formaldehyde to the nucleus isolation buffer), HMG B is not detected in micronuclei. Using polyclonal antibodies highly selective for HMG B, immunoblotting and immunofluorescence analyses show that the presence of HMG B in micronuclei is dynamic, correlating well with known periods of micronuclear DNA replication. This is the case not only during the vegetative cell cycle but also during early stages of the sexual cycle, conjugation, when the presence of HMG B in micronuclei is also closely correlated with meiotic DNA recombination and repair. Since micronuclei are transcriptionally inactive during vegetative growth, our data lend support to the idea that HMG B does not function exclusively in the establishment of transcriptionally competent chromatin. However, micronuclei are transcriptionally active during early stages of conjugation. Evidence that HMG B is strongly synthesized and deposited into micronuclei during this stage is presented. Therefore, it is tempting to suggest that HMG B may play an important role in remodeling micronuclear chromatin into an "active," more open configuration. We favor a model wherein HMG B, like other abundant, low-specificity HMG box-containing proteins, functions to wrap DNA, presumably modulating higher-order chromatin structure for a broad range of biological processes, including transcription and replication.

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31

Laux, Thomas, e Robert B. Goldberg. "A plant DNA binding protein shares highly conserved sequence motifs with HMG-box proteins". Nucleic Acids Research 19, n. 17 (1991): 4769. http://dx.doi.org/10.1093/nar/19.17.4769.

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32

Lavender, Paul, Laurence Vandel, Andrew J. Bannister e Tony Kouzarides. "The HMG-box transcription factor HBP1 is targeted by the pocket proteins and E1A". Oncogene 14, n. 22 (giugno 1997): 2721–28. http://dx.doi.org/10.1038/sj.onc.1201243.

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33

Philley, M. L., e C. Staben. "Functional analyses of the Neurospora crassa MT a-1 mating type polypeptide." Genetics 137, n. 3 (1 luglio 1994): 715–22. http://dx.doi.org/10.1093/genetics/137.3.715.

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Abstract (sommario):

Abstract The Neurospora crassa mt a-1 gene, encoding the MT a-1 polypeptide, determines a mating type properties: sexual compatibility and vegetative incompatibility with A mating type. We characterized in vivo and in vitro functions of the MT a-1 polypeptide and specific mutant derivatives. MT a-1 polypeptide produced in Escherichia coli bound to specific DNA sequences whose core was 5'-CTTTG-3'. DNA binding was a function of the MT a-1 HMG box domain (a DNA binding motif found in high mobility group proteins and a diverse set of regulatory proteins). Mutation within the HMG box eliminated DNA binding in vitro and eliminated mating in vivo, but did not interfere with vegetative incompatibility function in vivo. Conversely, deletion of amino acids 216-220 of MT a-1 eliminated vegetative incompatibility, but did not affect mating or DNA binding. Deletion of the carboxyl terminal half of MT a-1 eliminated both mating and vegetative incompatibility in vivo, but not DNA binding in vitro. These results suggest that mating depends upon the ability of MT a-1 polypeptide to bind to, and presumably to regulate the activity of, specific DNA sequences. However, the separation of vegetative incompatibility from both mating and DNA binding indicates that vegetative incompatibility functions by a biochemically distinct mechanism.

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34

Roy, Adrita, Arkajyoti Dutta, Dipan Roy, Payel Ganguly, Ritesh Ghosh, Rajiv K. Kar, Anirban Bhunia, Jayanta Mukhobadhyay e Shubho Chaudhuri. "Deciphering the role of the AT-rich interaction domain and the HMG-box domain of ARID-HMG proteins of Arabidopsis thaliana". Plant Molecular Biology 92, n. 3 (9 agosto 2016): 371–88. http://dx.doi.org/10.1007/s11103-016-0519-y.

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35

Kaur, Gurpreet, Aurelie Delluc-Clavieres, Ivan K. H. Poon, Jade K. Forwood, Dominic J. Glover e David A. Jans. "Calmodulin-dependent nuclear import of HMG-box family nuclear factors: importance of the role of SRY in sex reversal". Biochemical Journal 430, n. 1 (28 luglio 2010): 39–48. http://dx.doi.org/10.1042/bj20091758.

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Abstract (sommario):

The HMG (high-mobility group)-box-containing chromatin-remodelling factor SRY (sex-determining region on the Y chromosome) plays a key role in sex determination. Its role in the nucleus is critically dependent on two NLSs (nuclear localization signals) that flank its HMG domain: the C-terminally located ‘β-NLS’ that mediates nuclear transport through Impβ1 (importin β1) and the N-terminally located ‘CaM-NLS’ which is known to recognize the calcium-binding protein CaM (calmodulin). In the present study, we examined a number of missense mutations in the SRY CaM-NLS from human XY sex-reversed females for the first time, showing that they result in significantly reduced nuclear localization of GFP (green fluorescent protein)–SRY fusion proteins in transfected cells compared with wild-type. The CaM antagonist CDZ (calmidazolium chloride) was found to significantly reduce wild-type SRY nuclear accumulation, indicating dependence of SRY nuclear import on CaM. Intriguingly, the CaM-NLS mutants were all resistant to CDZ's effects, implying a loss of interaction with CaM, which was confirmed by direct binding experiments. CaM-binding/resultant nuclear accumulation was the only property of SRY found to be impaired by two of the CaM-NLS mutations, implying that inhibition of CaM-dependent nuclear import is the basis of sex reversal in these cases. Importantly, the CaM-NLS is conserved in other HMG-box-domain-containing proteins such as SOX-2, -9, -10 and HMGN1, all of which were found for the first time to rely on CaM for optimal nuclear localization. CaM-dependent nuclear translocation is thus a common mechanism for this family of important transcription factors.

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36

Snider, Lauren, Hilary Thirlwell, Jeffrey R. Miller, Randall T. Moon, Mark Groudine e Stephen J. Tapscott. "Inhibition of Tcf3 Binding by I-mfa Domain Proteins". Molecular and Cellular Biology 21, n. 5 (1 marzo 2001): 1866–73. http://dx.doi.org/10.1128/mcb.21.5.1866-1873.2001.

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ABSTRACT We have determined that I-mfa, an inhibitor of several basic helix-loop-helix (bHLH) proteins, and XIC, a Xenopusortholog of human I-mf domain-containing protein that shares a highly conserved cysteine-rich C-terminal domain with I-mfa, inhibit the activity and DNA binding of the HMG box transcription factor XTcf3. Ectopic expression of I-mfa or XIC in early Xenopus embryos inhibited dorsal axis specification, the expression of the Tcf3/β-catenin-regulated genessiamois and Xnr3, and the ability of β-catenin to activate reporter constructs driven by Lef/Tcf binding sites. I-mfa domain proteins can regulate both the Wnt signaling pathway and a subset of bHLH proteins, possibly coordinating the activities of these two critical developmental pathways.

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37

Sánchez-Giraldo, R., F. J. Acosta-Reyes, C. S. Malarkey, N. Saperas, M. E. A. Churchill e J. L. Campos. "Two high-mobility group box domains act together to underwind and kink DNA". Acta Crystallographica Section D Biological Crystallography 71, n. 7 (30 giugno 2015): 1423–32. http://dx.doi.org/10.1107/s1399004715007452.

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Abstract (sommario):

High-mobility group protein 1 (HMGB1) is an essential and ubiquitous DNA architectural factor that influences a myriad of cellular processes. HMGB1 contains two DNA-binding domains, box A and box B, which have little sequence specificity but have remarkable abilities to underwind and bend DNA. Although HMGB1 box A is thought to be responsible for the majority of HMGB1–DNA interactions with pre-bent or kinked DNA, little is known about how it recognizes unmodified DNA. Here, the crystal structure of HMGB1 box A bound to an AT-rich DNA fragment is reported at a resolution of 2 Å. Two box A domains of HMGB1 collaborate in an unusual configuration in which the Phe37 residues of both domains stack together and intercalate the same CG base pair, generating highly kinked DNA. This represents a novel mode of DNA recognition for HMGB proteins and reveals a mechanism by which structure-specific HMG boxes kink linear DNA.

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38

Kohler, A., M. S. Schmidt-Zachmann e W. W. Franke. "AND-1, a natural chimeric DNA-binding protein, combines an HMG-box with regulatory WD-repeats". Journal of Cell Science 110, n. 9 (1 maggio 1997): 1051–62. http://dx.doi.org/10.1242/jcs.110.9.1051.

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Using a specific monoclonal antibody (mAb AND-1/23-5-14) we have identified, cDNA-cloned and characterized a novel DNA-binding protein of the clawed toad, Xenopus laevis, that is accumulated in the nucleoplasm of oocytes and various other cells. This protein comprises 1,127 amino acids, with a total molecular mass of 125 kDa and a pI of 5.27. It is encoded by a mRNA of approximately 4 kb and contains, in addition to clusters of acidic amino acids, two hallmark motifs: the amino-terminal part harbours seven consecutive ‘WD-repeats’, which are sequence motifs of about 40 amino acids that are characteristic of a large group of regulatory proteins involved in diverse cellular functions, while the carboxy terminal portion possesses a 63-amino-acid-long ‘HMG-box’, which is typical of a family of DNA-binding proteins involved in regulation of chromatin assembly, transcription and replication. The DNA-binding capability of the protein was demonstrated by DNA affinity chromatography and electrophoretic mobility shift assays using four-way junction DNA. Protein AND-1 (acidic nucleoplasmic DNA-binding protein) appears as an oligomer, probably a homodimer, and has been localized throughout the entire interchromatinic space of the interphase nucleoplasm, whereas during mitosis it is transiently dispersed over the cytoplasm. We also identified a closely related, perhaps orthologous protein in mammals. The unique features of protein AND-1, which is a ‘natural chimera’ combining properties of the WD-repeat and the HMG-box families of proteins, are discussed in relation to its possible nuclear functions.

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39

Putnam, C. D., G. P. Copenhaver, M. L. Denton e C. S. Pikaard. "The RNA polymerase I transactivator upstream binding factor requires its dimerization domain and high-mobility-group (HMG) box 1 to bend, wrap, and positively supercoil enhancer DNA." Molecular and Cellular Biology 14, n. 10 (ottobre 1994): 6476–88. http://dx.doi.org/10.1128/mcb.14.10.6476.

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Upstream binding factor (UBF) is an important transactivator of RNA polymerase I and is a member of a family of proteins that contain nucleic acid binding domains named high-mobility-group (HMG) boxes because of their similarity to HMG chromosomal proteins. UBF is a highly sequence-tolerant DNA-binding protein for which no binding consensus sequence has been identified. Therefore, it has been suggested that UBF may recognize preformed structural features of DNA, a hypothesis supported by UBF's ability to bind synthetic DNA cruciforms, four-way junctions, and even tRNA. We show here that full-length UBF can also bend linear DNA to mediate circularization of probes as small as 102 bp in the presence of DNA ligase. Longer probes in the presence of UBF become positively supercoiled when ligated, suggesting that UBF wraps the DNA in a right-handed direction, opposite the direction of DNA wrapping around a nucleosome. The dimerization domain and HMG box 1 are necessary and sufficient to circularize short probes and supercoil longer probes in the presence of DNA ligase. UBF's sequence tolerance coupled with its ability to bend and wrap DNA makes UBF an unusual eukaryotic transcription factor. However, UBF's ability to bend DNA might explain how upstream and downstream rRNA gene promoter domains interact. UBF-induced DNA wrapping could also be a mechanism by which UBF counteracts histone-mediated gene repression.

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40

Putnam, C. D., G. P. Copenhaver, M. L. Denton e C. S. Pikaard. "The RNA polymerase I transactivator upstream binding factor requires its dimerization domain and high-mobility-group (HMG) box 1 to bend, wrap, and positively supercoil enhancer DNA". Molecular and Cellular Biology 14, n. 10 (ottobre 1994): 6476–88. http://dx.doi.org/10.1128/mcb.14.10.6476-6488.1994.

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Abstract (sommario):

Upstream binding factor (UBF) is an important transactivator of RNA polymerase I and is a member of a family of proteins that contain nucleic acid binding domains named high-mobility-group (HMG) boxes because of their similarity to HMG chromosomal proteins. UBF is a highly sequence-tolerant DNA-binding protein for which no binding consensus sequence has been identified. Therefore, it has been suggested that UBF may recognize preformed structural features of DNA, a hypothesis supported by UBF's ability to bind synthetic DNA cruciforms, four-way junctions, and even tRNA. We show here that full-length UBF can also bend linear DNA to mediate circularization of probes as small as 102 bp in the presence of DNA ligase. Longer probes in the presence of UBF become positively supercoiled when ligated, suggesting that UBF wraps the DNA in a right-handed direction, opposite the direction of DNA wrapping around a nucleosome. The dimerization domain and HMG box 1 are necessary and sufficient to circularize short probes and supercoil longer probes in the presence of DNA ligase. UBF's sequence tolerance coupled with its ability to bend and wrap DNA makes UBF an unusual eukaryotic transcription factor. However, UBF's ability to bend DNA might explain how upstream and downstream rRNA gene promoter domains interact. UBF-induced DNA wrapping could also be a mechanism by which UBF counteracts histone-mediated gene repression.

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41

Bakkaiova, Jana, Kosuke Arata, Miki Matsunobu, Bungo Ono, Tomoyo Aoki, Dana Lajdova, Martina Nebohacova, Jozef Nosek, Isamu Miyakawa e Lubomir Tomaska. "The Strictly Aerobic Yeast Yarrowia lipolytica Tolerates Loss of a Mitochondrial DNA-Packaging Protein". Eukaryotic Cell 13, n. 9 (27 giugno 2014): 1143–57. http://dx.doi.org/10.1128/ec.00092-14.

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Abstract (sommario):

ABSTRACT Mitochondrial DNA (mtDNA) is highly compacted into DNA-protein structures termed mitochondrial nucleoids (mt-nucleoids). The key mt-nucleoid components responsible for mtDNA condensation are HMG box-containing proteins such as mammalian mitochondrial transcription factor A (TFAM) and Abf2p of the yeast Saccharomyces cerevisiae . To gain insight into the function and organization of mt-nucleoids in strictly aerobic organisms, we initiated studies of these DNA-protein structures in Yarrowia lipolytica . We identified a principal component of mt-nucleoids in this yeast and termed it Yl Mhb1p ( Y . l ipolytica m itochondrial H MG b ox-containing protein 1). Yl Mhb1p contains two putative HMG boxes contributing both to DNA binding and to its ability to compact mtDNA in vitro . Phenotypic analysis of a Δ mhb1 strain lacking Yl Mhb1p resulted in three interesting findings. First, although the mutant exhibits clear differences in mt-nucleoids accompanied by a large decrease in the mtDNA copy number and the number of mtDNA-derived transcripts, its respiratory characteristics and growth under most of the conditions tested are indistinguishable from those of the wild-type strain. Second, our results indicate that a potential imbalance between subunits of the respiratory chain encoded separately by nuclear DNA and mtDNA is prevented at a (post)translational level. Third, we found that mtDNA in the Δ mhb1 strain is more prone to mutations, indicating that mtHMG box-containing proteins protect the mitochondrial genome against mutagenic events.

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42

Rhoades, Alison R., Susan Ruone e Tim Formosa. "Structural Features of Nucleosomes Reorganized by Yeast FACT and Its HMG Box Component, Nhp6". Molecular and Cellular Biology 24, n. 9 (1 maggio 2004): 3907–17. http://dx.doi.org/10.1128/mcb.24.9.3907-3917.2004.

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ABSTRACT The Saccharomyces cerevisiae Spt16/Cdc68, Pob3, and Nhp6 proteins (SPN or yFACT) bind to and alter nucleosomes in vitro, providing a potential explanation for their importance in both transcription and replication in vivo. We show that nucleosomes bound by either Nhp6 alone or the yFACT complex remain largely intact and immobile but are significantly reorganized, as indicated by changes in the pattern of sensitivity to DNase I and enhanced digestion by some restriction endonucleases. In contrast, yFACT enhanced access to exonuclease III only at very high levels of enzyme, suggesting that the DNA near the entry and exit sites of nucleosomes is largely unperturbed and that the position of the histone octamers relative to the DNA is not altered during reorganization. DNase I sensitivity was enhanced at sites clustered near the center of the nucleosomal DNA, away from the entry and exit points, and the pattern of nuclease sensitivity was only mildly affected by the configuration of linker extensions, further indicating that linkers play only a minor role in the reorganization of nucleosomes by yFACT. The DNA in contact with H2A-H2B dimers is therefore the region whose nuclease sensitivity was the least affected by yFACT reorganization. The most dramatic changes in nucleosome structure occurred when Spt16-Pob3 and the HMG box protein Nhp6 were both present, but Nhp6 alone altered DNase I sensitivity at some specific sites, supporting an independent role for this class of proteins in the general management of chromatin properties. yFACT activity does not require ATP hydrolysis and does not alter the position of nucleosomes, indicating that it acts through a mechanism distinct from chromatin remodeling. The results presented here suggest instead that yFACT promotes polymerase progression by reorganizing nucleosome cores into a less inhibitory conformation in which the properties of DNA sequences near the center of the nucleosomes are altered.

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43

Štros, M., D. Launholt e K. D. Grasser. "The HMG-box: a versatile protein domain occurring in a wide variety of DNA-binding proteins". Cellular and Molecular Life Sciences 64, n. 19-20 (29 giugno 2007): 2590–606. http://dx.doi.org/10.1007/s00018-007-7162-3.

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44

LAMBERTINI, Elisabetta, Letizia PENOLAZZI, Silvia GIORDANO, Laura DEL SENNO e Roberta PIVA. "Expression of the human oestrogen receptor-alpha gene is regulated by promoter F in MG-63 osteoblastic cells". Biochemical Journal 372, n. 3 (15 giugno 2003): 831–39. http://dx.doi.org/10.1042/bj20021633.

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Abstract (sommario):

(O)estrogen receptor-α (ERα), a hormone-dependent transcription factor belonging to the steroid/thyroid-hormone-receptor superfamily, plays an essential role in the development and maintenance of the skeleton. Here we report the analysis of an unexplored sequence inside the bone-specific distal promoter F (PF) with respect to the regulation of ERα gene expression in bone. This sequence, 785 bp in size, is localized upstream of the assigned transcription start site of exon F, at −117140 bp from the originally described transcription start site +1. It contains a TA reach box, a conventional CAAT box and potential regulatory elements for many transcription factors, including Cbfa1 [OSE2 (osteoblast-specific element) core binding factor], GATA-1 [(A/T)GATA(A/G) binding protein], Sox5 [sex-determining region Y (SRY)-type HMG bOX protein, belonging to a subfamily of DNA-binding proteins with an HMG domain], Sry, AP1 (activator protein 1) and CP2 (activator of γ-globin). It is able to strongly activate the luciferase reporter gene in MG-63 osteoblastic-like cells, but not in MCF7 breast-cancer cells. This is in agreement with different transcripts that we found in the two cell types. The footprinting and electrophoretic mobility-shift assays (EMSAs) showed that, inside the region analysed, there were some sequences that specifically reacted to nuclear proteins isolated from MG-63 cells. In particular, we identified two regions, named PFa and PFb, that do not present binding sites for known transcription factors and that are involved in a strong DNA–protein interaction in MG-63, but not in MCF7, cells. The analysis of three transcription factors (GATA-1, Sry and Sox) that might bind the identified footprinted areas suggested a possible indirect role of these proteins in the regulation of ERα gene expression in bone. These data provide evidence for different promoter usage of the ERα gene through the recruitment of tissue-specific transcription activators and co-regulators.

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45

Leger, H., E. Sock, K. Renner, F. Grummt e M. Wegner. "Functional interaction between the POU domain protein Tst-1/Oct-6 and the high-mobility-group protein HMG-I/Y." Molecular and Cellular Biology 15, n. 7 (luglio 1995): 3738–47. http://dx.doi.org/10.1128/mcb.15.7.3738.

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Abstract (sommario):

The POU domain protein Tst-1/Oct-6 is a transcriptional activator of human papovavirus JC virus in transient transfections. Because of its endogenous expression in myelinating glia, Tst-1/Oct-6 might also be an important determinant for the glia specificity of JC virus in vivo. Activation of viral early and late genes depends on the ability of Tst-1/Oct-6 to interact with an AT-rich element within the viral regulatory region. Here, we show that this element not only is bound by Tst-1/Oct-6 but, in addition, serves as a binding site for the high-mobility-group protein HMG-I/Y. In the presence of HMG-I/Y, Tst-1/Oct-6 exhibited an increased affinity for this AT-rich element. The specificity of this effect was evident from the fact that no stimulation of Tst-1/Oct-6 binding was observed on a site that did not allow binding of HMG-I/Y. In addition, both proteins interacted with each other in solution. Direct contacts were identified between the POU domain of Tst-1/Oct-6 and a short stretch of 10 amino acids in the central portion of HMG-I/Y. These results point to an accessory role for HMG-I/Y in the activation of JC viral gene expression by the POU domain protein Tst-1/Oct-6. In agreement with such a role, HMG-Y synergistically supported the function of Tst-1/Oct-6 in transient transfections, measured on the early promoter of JC virus or on an artificial promoter consisting of only a TATA box and the common binding element for Tst-1 and HMG-I/Y.

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46

Roy, Adrita, Arkajyoti Dutta, Dipan Roy, Payel Ganguly, Ritesh Ghosh, Rajiv K. Kar, Anirban Bhunia, Jayanta Mukhopadhyay e Shubho Chaudhuri. "Erratum to: Deciphering the role of the AT-rich interaction domain and the HMG-box domain of ARID-HMG proteins of Arabidopsis thaliana". Plant Molecular Biology 92, n. 3 (5 settembre 2016): 389–90. http://dx.doi.org/10.1007/s11103-016-0534-z.

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47

Borde, Chloé, Clémentine Dillard, Aurore L’Honoré, Frédérique Quignon, Marion Hamon, Christophe H. Marchand, Roberta Soares Faccion et al. "The C-Terminal Acidic Tail Modulates the Anticancer Properties of HMGB1". International Journal of Molecular Sciences 23, n. 14 (17 luglio 2022): 7865. http://dx.doi.org/10.3390/ijms23147865.

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Energy metabolism reprogramming was recently listed as a hallmark of cancer. In this process, the switch from pyruvate kinase isoenzyme type M1 to pyruvate kinase isoenzyme type M2 (PKM2) is believed to play a crucial role. Interestingly, the activity of the active form of PKM2 can efficiently be inhibited by the high-mobility group box 1 (HMGB1) protein, leading to a rapid blockage of glucose-dependent aerobic respiration and cancer cell death. HMGB1 is a member of the HMG protein family. It contains two DNA-binding HMG-box domains and an acidic C-terminal tail capable of positively or negatively modulating its biological properties. In this work, we report that the deletion of the C-terminal tail of HMGB1 increases its activity towards a large panel of cancer cells without affecting the viability of normal immortalized fibroblasts. Moreover, in silico analysis suggests that the truncated form of HMGB1 retains the capacity of the full-length protein to interact with PKM2. However, based on the capacity of the cells to circumvent oxidative phosphorylation inhibition, we were able to identify either a cytotoxic or cytostatic effect of the proteins. Together, our study provides new insights in the characterization of the anticancer activity of HMGB1.

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48

Taverna, Simona, Alessandro Tonacci, Maria Ferraro, Giuseppe Cammarata, Giuseppina Cuttitta, Salvatore Bucchieri, Elisabetta Pace e Sebastiano Gangemi. "High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases". Cells 11, n. 5 (1 marzo 2022): 849. http://dx.doi.org/10.3390/cells11050849.

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In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

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49

Wang, Jianyang, Valeria Pappas-Brown, Paul T. Englund e Robert E. Jensen. "TbKAP6, a Mitochondrial HMG Box-Containing Protein in Trypanosoma brucei, Is the First Trypanosomatid Kinetoplast-Associated Protein Essential for Kinetoplast DNA Replication and Maintenance". Eukaryotic Cell 13, n. 7 (30 maggio 2014): 919–32. http://dx.doi.org/10.1128/ec.00260-13.

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ABSTRACT Kinetoplast DNA (kDNA), the mitochondrial genome of trypanosomatids, is a giant planar network of catenated minicircles and maxicircles. In vivo kDNA is organized as a highly condensed nucleoprotein disk. So far, in Trypanosoma brucei , proteins involved in the maintenance of the kDNA condensed structure remain poorly characterized. In Crithidia fasciculata , some small basic histone H1-like k inetoplast- a ssociated p roteins (CfKAP) have been shown to condense isolated kDNA networks in vitro . High-mobility group (HMG) box-containing proteins, such as mitochondrial transcription factor A (TFAM) in mammalian cells and Abf2 in the budding yeast, have been shown essential for the packaging of mitochondrial DNA (mtDNA) into mitochondrial nucleoids, remodeling of mitochondrial nucleoids, gene expression, and maintenance of mtDNA. Here, we report that TbKAP6, a mitochondrial HMG box-containing protein, is essential for parasite cell viability and involved in kDNA replication and maintenance. The RNA interference (RNAi) depletion of TbKAP6 stopped cell growth. Replication of both minicircles and maxicircles was inhibited. RNAi or overexpression of TbKAP6 resulted in the disorganization, shrinkage, and loss of kDNA. Minicircle release, the first step in kDNA replication, was inhibited immediately after induction of RNAi, but it quickly increased 3-fold upon overexpression of TbKAP6. Since the release of covalently closed minicircles is mediated by a type II topoisomerase (topo II), we examined the potential interactions between TbKAP6 and topo II. Recombinant TbKAP6 (rTbKAP6) promotes the topo II-mediated decatenation of kDNA. rTbKAP6 can condense isolated kDNA networks in vitro . These results indicate that TbKAP6 is involved in the replication and maintenance of kDNA.

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Hett, Anne Kathrin, e Arne Ludwig. "SRY-related (Sox) genes in the genome of European Atlantic sturgeon (Acipenser sturio)". Genome 48, n. 2 (1 aprile 2005): 181–86. http://dx.doi.org/10.1139/g04-112.

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The Sox-gene family represents an ancient group of transcription factors involved in numerous developmental processes and sex determination in vertebrates. SOX proteins are characterized by a conserved high mobility group (HMG)-box domain, which is responsible for DNA binding and bending. We studied Sox genes in sturgeon, one of the most primitive groups of fishes characterized by a high chromosome number. Male and female genomes were screened for Sox genes using highly degenerate primers that amplified a broad range of HMG boxes. A total of 102 clones, representing 22 different sequences coding for 8 Sox genes, was detected and classified according to their orthologues. Sox2, Sox3, Sox4, Sox9, Sox11, Sox17, Sox19, and Sox21 were found in sturgeon; these genes represent Sox groups B, C, E, and F. In a phylogenetic analysis (neighbor-joining, maximum likelihood, maximum parsimony), these genes clustered with their mouse orthologues. In the case of Sox4, Sox17, and Sox21, we found evidence of gene duplication.Key words: Acipenseridae, gene evolution, sex determination, Sox genes.

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