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1
Csigi, Péter. « Aquileiai Chromatius Máté-evangéliumhoz írt kommentárja ». Vallástudományi Szemle 20, no 1 (2024) : 9–32. https://doi.org/10.55193/rs.2024.1.9.
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A Szentírás értelmezése kezdettől fogva komoly kihívás elé állította az Egyházat. Főképp a különféle eretnekmozgalmak feltűnése tette szükségessé, hogy világosan megkülönböztessék, melyik az az írásmagyarázati tradíció, amely kifejezi és hordozza az Egyház hitét. Az Írás értelmezésének nemcsak tudományos vagy apologetikus céljai voltak, hanem mindenekelőtt a keresztény hívek lelkének táplálása, hitük megerősítése. Ezen a téren kitűntek azok a püspökök, akik egy-egy helyi egyház élén állva felelősséget éreztek a rájuk bízott nyáj iránt. Ezek sorába illeszkedik Chromatius, Aquileia IV. századi püspöke, aki bár a saját korában méltán nagy tiszteletnek és ismertségnek örvendő főpap volt, a legújabb korra neve mégis majdnem feledésbe merült. A megismerésre pedig érdemessé teszi Chromatius püspököt Jeromoshoz és Rufinushoz fűződő barátsága mellett kikezdhetetlen ortodox hite, kitűnő stílusa és lelkipásztori érzékenysége. Jelen tanulmány témája Chromatius legfontosabb művének, a töredékesen fennmaradt Máté-evangéliumhoz írt kommentárnak a bemutatása.
2
McEachnie, Robert. « A History of Heresy Past : The Sermons of Chromatius of Aquileia, 388–407 ». Church History 83, no 2 (27 mai 2014) : 273–96. http://dx.doi.org/10.1017/s0009640714000031.
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Chromatius served as bishop of Aquileia, a large trade-centered city at the north end of the Adriatic Sea, from 388–407. He interacted with notables like Rufinus, Jerome, Ambrose, and John Chrysostom, but our knowledge of Chromatius was limited to second-hand statements until the rediscovery of his sermons in the last century. When one examines the sermons in their original context, a disconnect on the issue of heresy emerges. Based on a survey of Christianities in northern Italy, it seems that the variety we might expect is lacking in the sources. An examination of the region reveals that the area during this time was remarkably homogenous in terms of the diversity among its Christian adherents. In Aquileia, Chromatius would have been unchallenged by other churches. In light of that, what did his continued tirades against non-existent “heretical” groups achieve? By examining the whole of each sermon mentioning heretics a pattern emerges surrounding the history of heresy and orthodoxy. The maintenance of institutional memory was not done sentimentally, but to advance the domination Christians had achieved into new arenas, namely, for Chromatius, control over an urban religious space which included Judaism.
3
Sajovic, Miran. « “Sermo eorum sicut cancer serpit”. Chromatius of Aquileia against heresies ». Vox Patrum 68 (16 décembre 2018) : 443–55. http://dx.doi.org/10.31743/vp.3369.
Texte intégralRésumé :
Bishop Chromatius (in office from 388 to 407), whose episcopal see was a cosmopolitan trade-center at the north end of the Adriatic Sea with the name of Aquileia, was one of the most prominent bishops in the period. He is acquainted with notable figures such as Ambrosius, Hieronymus, Rufinus, and Ioannes Chrysostomus and forth. Before being created a bishop, he was the secretary of bishop Valerianus and in the occasion of Council of Aquileia in 381, he had spoken against Arians. This Council was presided by Ambrosius and with its scale it could almost be considered as an ecumenical one. As shown in some of the Chromatius’ sermons, which are unearthed in the 20th century, he opposed not only to the ideas of Arians but also to the teaching of Fotinus, bishop of Sirmium. Chromatius was a very zealous fighter and he practically succeeded to uproot all heretical ideas in his diocese. The academia usually sees him as an anti-Arian theologian. After the Council of Constantinople (381), the Arian heresy seemed to be abated, but Chromatius said in one of his Tractatus, “Cuius (sc. Arii) discipuli hodieque oues Dei fallere ac decipere conantur per aliquantas ecclesias, sed iamdudum, magistro perfidiae prodito, discipuli latere non possunt”; it is evident that, the followers of Arius could still be found (with the mentioning of “hodie”, i.e. today) in the area of Aquileia, meanwhile one must not neglect the presence of the followers of Fotinus of Sirmium. The first part of my conference paper would be a general presentation of the religious situation in Aquileia at the time where Chromatius served as the local bishop; thus I will proceed with an in-depth reading on several passages of the Aquilerian bishop’s sermons (Sermones and Tractatus), in order to show the impact of the those heresies on his works and to identity his theological arguments against them. Among those teachings, there is the “unconquerable faith (invicta fide)”, which led to the surmounting (suppression) of heresies.
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Peressotti, Giuseppe. « La Madre di Cristo nelle opere dei Padri aquileiesi ». Augustinianum 63, no 1 (2023) : 109–29. http://dx.doi.org/10.5840/agstm20236314.
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This article deals with Mariology as we can deduce it from the works of writers who lived in the region of Aquileia in the 4th and 5th centuries. The first part of the study discusses the Gospel commentary by Fortunatianus and the works of Chromatius, bishops of Aquileia. The second part of the article considers texts excerpted from works on the same subject by Victorinus of Pettau, Rufinus of Concordia and Jerome of Stridon. The prevailent titles used of Mary are «Virgin» and «Mother of God». The article concludes with a comparison among significative texts excerpted from works of Chromatius and that of Rufinus.
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Peressotti, Giuseppe. « Demonologia in area aquileiese ». Augustinianum 59, no 1 (2019) : 101–27. http://dx.doi.org/10.5840/agstm20195915.
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The present work focuses on some particular demonological texts attributed to Fortunatianus (mid-IV century) and Chromatius (between the IV and the V century), both bishops of Aquileia. It also includes Victorinus, bishop of Poetovium (in present-day Slovenia, second half of the III century), who shared the same geographical-cultural milieu of the Aquilean bishops. We have considered primarily their biblical commentaries and, in the case of Chromatius, also his liturgical sermons. In these texts, the devil is characterized by a broad range of expressions in relation to his spiritual struggle against humanity, a struggle already won by Jesus and now entrusted to Christians. The three bishops highlight both the devil’s ability to deceive the sons of God, leading them to idolatry and heresy, and also the victory over him achieved by means of evangelical preaching.
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Beatrice, Pier Franco. « Chromatius and Jovinus at the Synod of Diospolis : A Prosopographical Inquiry ». Journal of Early Christian Studies 22, no 3 (2014) : 437–64. http://dx.doi.org/10.1353/earl.2014.0039.
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Giménez-Abián, J. F., D. J. Clarke, A. M. Mullinger, C. S. Downes et R. T. Johnson. « A postprophase topoisomerase II-dependent chromatid core separation step in the formation of metaphase chromosomes. » Journal of Cell Biology 131, no 1 (1 octobre 1995) : 7–17. http://dx.doi.org/10.1083/jcb.131.1.7.
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Metaphase chromatids are believed to consist of loops of chromatin anchored to a central scaffold, of which a major component is the decatenatory enzyme DNA topoisomerase II. Silver impregnation selectively stains an axial element of metaphase and anaphase chromatids; but we find that in earlier stages of mitosis, silver staining reveals an initially single, folded midline structure, which separates at prometaphase to form two chromatid axes. Inhibition of topoisomerase II prevents this separation, and also prevents the contraction of chromatids that occurs when metaphase is arrested. Immunolocalization of topoisomerase II alpha reveals chromatid cores analogous to those seen with silver staining. We conclude that the chromatid cores in early mitosis form a single structure, constrained by DNA catenations, which must separate before metaphase chromatids can be resolved.
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Daban, Joan-Ramon. « The energy components of stacked chromatin layers explain the morphology, dimensions and mechanical properties of metaphase chromosomes ». Journal of The Royal Society Interface 11, no 92 (6 mars 2014) : 20131043. http://dx.doi.org/10.1098/rsif.2013.1043.
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The measurement of the dimensions of metaphase chromosomes in different animal and plant karyotypes prepared in different laboratories indicates that chromatids have a great variety of sizes which are dependent on the amount of DNA that they contain. However, all chromatids are elongated cylinders that have relatively similar shape proportions (length to diameter ratio approx. 13). To explain this geometry, it is considered that chromosomes are self-organizing structures formed by stacked layers of planar chromatin and that the energy of nucleosome–nucleosome interactions between chromatin layers inside the chromatid is approximately 3.6 × 10 −20 J per nucleosome, which is the value reported by other authors for internucleosome interactions in chromatin fibres. Nucleosomes in the periphery of the chromatid are in contact with the medium; they cannot fully interact with bulk chromatin within layers and this generates a surface potential that destabilizes the structure. Chromatids are smooth cylinders because this morphology has a lower surface energy than structures having irregular surfaces. The elongated shape of chromatids can be explained if the destabilizing surface potential is higher in the telomeres (approx. 0.16 mJ m −2 ) than in the lateral surface (approx. 0.012 mJ m −2 ). The results obtained by other authors in experimental studies of chromosome mechanics have been used to test the proposed supramolecular structure. It is demonstrated quantitatively that internucleosome interactions between chromatin layers can justify the work required for elastic chromosome stretching (approx. 0.1 pJ for large chromosomes). The high amount of work (up to approx. 10 pJ) required for large chromosome extensions is probably absorbed by chromatin layers through a mechanism involving nucleosome unwrapping.
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Mishra, Prashant K., Sultan Ciftci-Yilmaz, David Reynolds, Wei-Chun Au, Lars Boeckmann, Lauren E. Dittman, Ziad Jowhar et al. « Polo kinase Cdc5 associates with centromeres to facilitate the removal of centromeric cohesin during mitosis ». Molecular Biology of the Cell 27, no 14 (15 juillet 2016) : 2286–300. http://dx.doi.org/10.1091/mbc.e16-01-0004.
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Sister chromatid cohesion is essential for tension-sensing mechanisms that monitor bipolar attachment of replicated chromatids in metaphase. Cohesion is mediated by the association of cohesins along the length of sister chromatid arms. In contrast, centromeric cohesin generates intrastrand cohesion and sister centromeres, while highly cohesin enriched, are separated by >800 nm at metaphase in yeast. Removal of cohesin is necessary for sister chromatid separation during anaphase, and this is regulated by evolutionarily conserved polo-like kinase (Cdc5 in yeast, Plk1 in humans). Here we address how high levels of cohesins at centromeric chromatin are removed. Cdc5 associates with centromeric chromatin and cohesin-associated regions. Maximum enrichment of Cdc5 in centromeric chromatin occurs during the metaphase-to-anaphase transition and coincides with the removal of chromosome-associated cohesin. Cdc5 interacts with cohesin in vivo, and cohesin is required for association of Cdc5 at centromeric chromatin. Cohesin removal from centromeric chromatin requires Cdc5 but removal at distal chromosomal arm sites does not. Our results define a novel role for Cdc5 in regulating removal of centromeric cohesins and faithful chromosome segregation.
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Chen, Yu-Fan, Chia-Ching Chou et Marc R. Gartenberg. « Determinants of Sir2-Mediated, Silent Chromatin Cohesion ». Molecular and Cellular Biology 36, no 15 (16 mai 2016) : 2039–50. http://dx.doi.org/10.1128/mcb.00057-16.
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Cohesin associates with distinct sites on chromosomes to mediate sister chromatid cohesion. Single cohesin complexes are thought to bind by encircling both sister chromatids in a topological embrace. Transcriptionally repressed chromosomal domains in the yeastSaccharomyces cerevisiaerepresent specialized sites of cohesion where cohesin binds silent chromatin in a Sir2-dependent fashion. In this study, we investigated the molecular basis for Sir2-mediated cohesion. We identified a cluster of charged surface residues of Sir2, collectively termed the EKDK motif, that are required for cohesin function. In addition, we demonstrated that Esc8, a Sir2-interacting factor, is also required for silent chromatin cohesion. Esc8 was previously shown to associate with Isw1, the enzymatic core of ISW1 chromatin remodelers, to form a variant of the ISW1a chromatin remodeling complex. WhenESC8was deleted or the EKDK motif was mutated, cohesin binding at silenced chromatin domains persisted but cohesion of the domains was abolished. The data are not consistent with cohesin embracing both sister chromatids within silent chromatin domains. Transcriptional silencing remains largely intact in strains lackingESC8or bearing EKDK mutations, indicating that silencing and cohesion are separable functions of Sir2 and silent chromatin.
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Sapkota, Hem, Emilia Wasiak, John R. Daum et Gary J. Gorbsky. « Multiple determinants and consequences of cohesion fatigue in mammalian cells ». Molecular Biology of the Cell 29, no 15 (août 2018) : 1811–24. http://dx.doi.org/10.1091/mbc.e18-05-0315.
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Cells delayed in metaphase with intact mitotic spindles undergo cohesion fatigue, where sister chromatids separate asynchronously, while cells remain in mitosis. Cohesion fatigue requires release of sister chromatid cohesion. However, the pathways that breach sister chromatid cohesion during cohesion fatigue remain unknown. Using moderate-salt buffers to remove loosely bound chromatin cohesin, we show that “cohesive” cohesin is not released during chromatid separation during cohesion fatigue. Using a regulated protein heterodimerization system to lock different cohesin ring interfaces at specific times in mitosis, we show that the Wapl-mediated pathway of cohesin release is not required for cohesion fatigue. By manipulating microtubule stability and cohesin complex integrity in cell lines with varying sensitivity to cohesion fatigue, we show that rates of cohesion fatigue reflect a dynamic balance between spindle pulling forces and resistance to separation by interchromatid cohesion. Finally, while massive separation of chromatids in cohesion fatigue likely produces inviable cell progeny, we find that short metaphase delays, leading to partial chromatid separation, predispose cells to chromosome missegregation. Thus, complete separation of one or a few chromosomes and/or partial separation of sister chromatids may be an unrecognized but common source of chromosome instability that perpetuates the evolution of malignant cells in cancer.
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Stanyte, Rugile, Johannes Nuebler, Claudia Blaukopf, Rudolf Hoefler, Roman Stocsits, Jan-Michael Peters et Daniel W. Gerlich. « Dynamics of sister chromatid resolution during cell cycle progression ». Journal of Cell Biology 217, no 6 (25 avril 2018) : 1985–2004. http://dx.doi.org/10.1083/jcb.201801157.
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Faithful genome transmission in dividing cells requires that the two copies of each chromosome’s DNA package into separate but physically linked sister chromatids. The linkage between sister chromatids is mediated by cohesin, yet where sister chromatids are linked and how they resolve during cell cycle progression has remained unclear. In this study, we investigated sister chromatid organization in live human cells using dCas9-mEGFP labeling of endogenous genomic loci. We detected substantial sister locus separation during G2 phase irrespective of the proximity to cohesin enrichment sites. Almost all sister loci separated within a few hours after their respective replication and then rapidly equilibrated their average distances within dynamic chromatin polymers. Our findings explain why the topology of sister chromatid resolution in G2 largely reflects the DNA replication program. Furthermore, these data suggest that cohesin enrichment sites are not persistent cohesive sites in human cells. Rather, cohesion might occur at variable genomic positions within the cell population.
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Zgraja, Brunon. « Zagadnienie wiary w nauczaniu kaznodziejskim św. Chromacjusza z Akwilei ». Vox Patrum 61 (5 janvier 2014) : 467–78. http://dx.doi.org/10.31743/vp.3639.
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St. Chromatius, bishop of Aquileia, who lived at the turn of the IV and V century, as a zealous pastor, led by concern for the salvation of his faithful, undertook in his predicatory teaching an explanation of the queations of faith. Without indications of any polemics – as one might expect – with the Arianism which was spread through the Gothic invaders, he did it, not ignoring however the important doctrinal aspect which constitutes the basis of the act of faith. He teaches, that to believe means to walk incessantly the Christ’s way of righteousness, know thanks to the proclaimed Gospel. Receiving the holy baptism is the beginning of that way. In a simple, but interesting at the same time, preaching being not infrequently the fruit of an allegorical, often amazing interpretation of the Bible events and signs know to his listeners, the bishop of Aquileia furthermore encourages to fidelity to the chosen way of righteousness, making his listeners aware that walking this way means not only walking a way that is free from wrongdoing, which brings concrete fruits, of which the most valuable is the eternal salvation. Being aware of many menaces in spiritual life, he also warns in his sermons against the danger of losing the faith.
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Jack, E. M., C. J. Harrison, G. R. White, C. H. Ockey et T. D. Allen. « Fine-structural aspects of bromodeoxyuridine incorporation in sister chromatid differentiation and replication banding ». Journal of Cell Science 94, no 2 (1 octobre 1989) : 287–97. http://dx.doi.org/10.1242/jcs.94.2.287.
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The structure of harlequin-stained chromosomes following substitution with low levels of 5-bromodeoxyuridine (BrdUrd) over two cell cycles and high levels over the last part of one cycle (replication banding) was studied in Chinese hamster ovary (CHO) cells. By using correlative light (LM) and scanning electron microscopy (SEM), it was shown that the effects of both the ultraviolet light (u.v.) and hot SSC treatment steps of the harlequin staining procedure were necessary to obtain sister-chromatid differentiation (SCD) or replication banding. u.v. treatment alone resulted in dark Giemsa staining of both chromatids with SEM morphology of short compact protuberances and an overall flattened smooth appearance in both the unsubstituted and BrdUrd-substituted chromatids, a morphology essentially similar to that of untreated chromosomes. SSC alone on the other hand resulted in dark-staining chromatids with an SEM morphology of raised, loosely packed loops of fibres in both types of chromatids. u.v. and SSC treatment together resulted in differentiation, with dark-staining unifilarly (TB) chromatids in the LM corresponding to raised loosely packed loops in the SEM and pale bifilarly (BB) chromatids corresponding to the smooth compact flattened SEM appearance. Where the BrdUrd-substituted strand became the template (BT), or when the nascent strand TB contained high levels of BrdUrd substitution in replication banding, the chromatid stained pale and showed the compact smooth appearance in the SEM. The Giemsa staining ability and ultrastructural morphology of harlequin staining is discussed with respect to putative DNA loss and also in terms of preferential protein-protein, protein-DNA cross-linkage in BrdUrd-containing DNA. These changes are also compared with the ultrastructural morphology observed after other banding methods, where deterioration of protein and DNA-protein interaction resulting in aggregation of chromatin fibres appears to be the major mechanism.
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Salzman, Michele Renee. « Chromatius of Aquileia and the Making of a Christian City. By Robert McEachnie. New York : Routledge, 2017. ix + 194 pp. $155.00 cloth. » Church History 88, no 3 (septembre 2019) : 796–98. http://dx.doi.org/10.1017/s0009640719002014.
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Samejima, Kumiko, Itaru Samejima, Paola Vagnarelli, Hiromi Ogawa, Giulia Vargiu, David A. Kelly, Flavia de Lima Alves et al. « Mitotic chromosomes are compacted laterally by KIF4 and condensin and axially by topoisomerase IIα ». Journal of Cell Biology 199, no 5 (19 novembre 2012) : 755–70. http://dx.doi.org/10.1083/jcb.201202155.
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Mitotic chromosome formation involves a relatively minor condensation of the chromatin volume coupled with a dramatic reorganization into the characteristic “X” shape. Here we report results of a detailed morphological analysis, which revealed that chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms. In this analysis, KIF4 and condensin were mutually dependent for their dynamic localization on the chromatid axes. Depletion of either caused sister chromatids to expand and compromised the “intrinsic structure” of the chromosomes (defined in an in vitro assay), with loss of condensin showing stronger effects. Simultaneous depletion of KIF4 and condensin caused complete loss of chromosome morphology. In these experiments, topoisomerase IIα contributed to shaping mitotic chromosomes by promoting the shortening of the chromatid axes and apparently acting in opposition to the actions of KIF4 and condensins. These three proteins are major determinants in shaping the characteristic mitotic chromosome morphology.
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Lica, L. M., S. Narayanswami et B. A. Hamkalo. « Mouse satellite DNA, centromere structure, and sister chromatid pairing. » Journal of Cell Biology 103, no 4 (1 octobre 1986) : 1145–51. http://dx.doi.org/10.1083/jcb.103.4.1145.
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The experiments described were directed toward understanding relationships between mouse satellite DNA, sister chromatid pairing, and centromere function. Electron microscopy of a large mouse L929 marker chromosome shows that each of its multiple constrictions is coincident with a site of sister chromatid contact and the presence of mouse satellite DNA. However, only one of these sites, the central one, possesses kinetochores. This observation suggests either that satellite DNA alone is not sufficient for kinetochore formation or that when one kinetochore forms, other potential sites are suppressed. In the second set of experiments, we show that highly extended chromosomes from Hoechst 33258-treated cells (Hilwig, I., and A. Gropp, 1973, Exp. Cell Res., 81:474-477) lack kinetochores. Kinetochores are not seen in Miller spreads of these chromosomes, and at least one kinetochore antigen is not associated with these chromosomes when they were subjected to immunofluorescent analysis using anti-kinetochore scleroderma serum. These data suggest that kinetochore formation at centromeric heterochromatin may require a higher order chromatin structure which is altered by Hoechst binding. Finally, when metaphase chromosomes are subjected to digestion by restriction enzymes that degrade the bulk of mouse satellite DNA, contact between sister chromatids appears to be disrupted. Electron microscopy of digested chromosomes shows that there is a significant loss of heterochromatin between the sister chromatids at paired sites. In addition, fluorescence microscopy using anti-kinetochore serum reveals a greater inter-kinetochore distance than in controls or chromosomes digested with enzymes that spare satellite. We conclude that the presence of mouse satellite DNA in these regions is necessary for maintenance of contact between the sister chromatids of mouse mitotic chromosomes.
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Henrikus, Sarah S., et Alessandro Costa. « Towards a Structural Mechanism for Sister Chromatid Cohesion Establishment at the Eukaryotic Replication Fork ». Biology 10, no 6 (26 mai 2021) : 466. http://dx.doi.org/10.3390/biology10060466.
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Cohesion between replicated chromosomes is essential for chromatin dynamics and equal segregation of duplicated genetic material. In the G1 phase, the ring-shaped cohesin complex is loaded onto duplex DNA, enriching at replication start sites, or “origins”. During the same phase of the cell cycle, and also at the origin sites, two MCM helicases are loaded as symmetric double hexamers around duplex DNA. During the S phase, and through the action of replication factors, cohesin switches from encircling one parental duplex DNA to topologically enclosing the two duplicated DNA filaments, which are known as sister chromatids. Despite its vital importance, the structural mechanism leading to sister chromatid cohesion establishment at the replication fork is mostly elusive. Here we review the current understanding of the molecular interactions between the replication machinery and cohesin, which support sister chromatid cohesion establishment and cohesin function. In particular, we discuss how cryo-EM is shedding light on the mechanisms of DNA replication and cohesin loading processes. We further expound how frontier cryo-EM approaches, combined with biochemistry and single-molecule fluorescence assays, can lead to understanding the molecular basis of sister chromatid cohesion establishment at the replication fork.
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McNicoll, François, Anne Kühnel, Uddipta Biswas, Kai Hempel, Gabriela Whelan, Gregor Eichele et Rolf Jessberger. « Meiotic sex chromosome cohesion and autosomal synapsis are supported by Esco2 ». Life Science Alliance 3, no 3 (12 février 2020) : e201900564. http://dx.doi.org/10.26508/lsa.201900564.
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In mitotic cells, establishment of sister chromatid cohesion requires acetylation of the cohesin subunit SMC3 (acSMC3) by ESCO1 and/or ESCO2. Meiotic cohesin plays additional but poorly understood roles in the formation of chromosome axial elements (AEs) and synaptonemal complexes. Here, we show that levels of ESCO2, acSMC3, and the pro-cohesion factor sororin increase on meiotic chromosomes as homologs synapse. These proteins are less abundant on the largely unsynapsed sex chromosomes, whose sister chromatid cohesion appears weaker throughout the meiotic prophase. Using three distinct conditional Esco2 knockout mouse strains, we demonstrate that ESCO2 is essential for male gametogenesis. Partial depletion of ESCO2 in prophase I spermatocytes delays chromosome synapsis and further weakens cohesion along sex chromosomes, which show extensive separation of AEs into single chromatids. Unsynapsed regions of autosomes are associated with the sex chromatin and also display split AEs. This study provides the first evidence for a specific role of ESCO2 in mammalian meiosis, identifies a particular ESCO2 dependence of sex chromosome cohesion and suggests support of autosomal synapsis by acSMC3-stabilized cohesion.
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Nakamura, Akito, Hiroyuki Arai et Naoya Fujita. « Centrosomal Aki1 and cohesin function in separase-regulated centriole disengagement ». Journal of Cell Biology 187, no 5 (23 novembre 2009) : 607–14. http://dx.doi.org/10.1083/jcb.200906019.
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Sister chromatid separation at anaphase is triggered by cleavage of the cohesin subunit Scc1, which is mediated by separase. Centriole disengagement also requires separase. This dual role of separase permits concurrent control of these events for accurate metaphase to anaphase transition. Although the molecular mechanism underlying sister chromatid cohesion has been clarified, that of centriole cohesion is poorly understood. In this study, we show that Akt kinase–interacting protein 1 (Aki1) localizes to centrosomes and regulates centriole cohesion. Aki1 depletion causes formation of multipolar spindles accompanied by centriole splitting, which is separase dependent. We also show that cohesin subunits localize to centrosomes and that centrosomal Scc1 is cleaved by separase coincidentally with chromatin Scc1, suggesting a role of Scc1 as a connector of centrioles as well as sister chromatids. Interestingly, Scc1 depletion strongly induces centriole splitting. Furthermore, Aki1 interacts with cohesin in centrosomes, and this interaction is required for centriole cohesion. We demonstrate that centrosome-associated Aki1 and cohesin play pivotal roles in preventing premature cleavage in centriole cohesion.
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Gallego-Paez, Lina Marcela, Hiroshi Tanaka, Masashige Bando, Motoko Takahashi, Naohito Nozaki, Ryuichiro Nakato, Katsuhiko Shirahige et Toru Hirota. « Smc5/6-mediated regulation of replication progression contributes to chromosome assembly during mitosis in human cells ». Molecular Biology of the Cell 25, no 2 (15 janvier 2014) : 302–17. http://dx.doi.org/10.1091/mbc.e13-01-0020.
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The structural maintenance of chromosomes (SMC) proteins constitute the core of critical complexes involved in structural organization of chromosomes. In yeast, the Smc5/6 complex is known to mediate repair of DNA breaks and replication of repetitive genomic regions, including ribosomal DNA loci and telomeres. In mammalian cells, which have diverse genome structure and scale from yeast, the Smc5/6 complex has also been implicated in DNA damage response, but its further function in unchallenged conditions remains elusive. In this study, we addressed the behavior and function of Smc5/6 during the cell cycle. Chromatin fractionation, immunofluorescence, and live-cell imaging analyses indicated that Smc5/6 associates with chromatin during interphase but largely dissociates from chromosomes when they condense in mitosis. Depletion of Smc5 and Smc6 resulted in aberrant mitotic chromosome phenotypes that were accompanied by the abnormal distribution of topoisomerase IIα (topo IIα) and condensins and by chromosome segregation errors. Importantly, interphase chromatin structure indicated by the premature chromosome condensation assay suggested that Smc5/6 is required for the on-time progression of DNA replication and subsequent binding of topo IIα on replicated chromatids. These results indicate an essential role of the Smc5/6 complex in processing DNA replication, which becomes indispensable for proper sister chromatid assembly in mitosis.
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Quinn, Dennis P. « Chromatius of Aquileia and His Age : Proceedings of the International Conference Held in Aquileia, 22-24 May 2008 - Edited by Pier Franco Beatrice and Alessio Peršič ». Religious Studies Review 38, no 1 (mars 2012) : 25. http://dx.doi.org/10.1111/j.1748-0922.2011.01579_9.x.
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Sorsa, V. « Distribution of chromomeres as a basis of chromosomal coiling ». Journal of Cell Science 80, no 1 (1 février 1986) : 193–205. http://dx.doi.org/10.1242/jcs.80.1.193.
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Periodicity in the distribution of prominent bands was analysed from the light and electron microscopic maps of salivary gland chromosomes of Drosophila melanogaster. The data obtained indicate that a similar distribution of prominent chromosomes in an individual interphase chromatid results in a unilateral accumulation of chromatin at the chromonema stage, if the helical axis of chromonema consists of approximately 5–9 interchromomere + chromomere units per turn. Orientation of the largest chromomeres mainly on one lateral half and the smallest chromomeres mainly on the opposite lateral half of the chromonema apparently bends it to form the chromosomal ‘macro’ coil. Thus the increase in DNA content in the chromomeric loops located at specific intervals along the chromatids may have an important role in the evolution of coiling hierarchy in the eukaryotic chromosomes.
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Uchiyama, Susumu, et Kiichi Fukui. « Condensin in Chromatid Cohesion and Segregation ». Cytogenetic and Genome Research 147, no 4 (2015) : 212–16. http://dx.doi.org/10.1159/000444868.
Texte intégralRésumé :
After replication of genomic DNA during the S phase, 2 chromatids hold together longitudinally. When cells enter mitosis, the paired sister chromatids start to condense and then segregate into individual chromatids except for the centromeric region. Upon attachment of microtubules to the kinetochore, subsequent pulling of the 2 sister chromatids by the spindles towards opposite poles results in 2 completely separated chromatids. Besides more than 100 kinds of kinetochore proteins, several key proteins such as cohesin, separase, shugoshin, and condensin contribute to chromatid cohesion and segregation. Among these proteins, condensin, a protein complex composed of 5 subunits discovered 2 decades ago, has been extensively studied in terms of the maintenance of chromosome morphology as its major function. Recent studies on condensin uncovered its role in chromatid cohesion and segregation, which will be reviewed in this article.
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Fujii, Wataru, et Hiroaki Funahashi. « In vitro development of non-enucleated rat oocytes following microinjection of a cumulus nucleus and chemical activation ». Zygote 16, no 2 (mai 2008) : 117–25. http://dx.doi.org/10.1017/s0967199408004632.
Texte intégralRésumé :
SummaryThe present study examined in vitro development and the cytological status of non-enucleated rat oocytes after microinjection of cumulus nuclei and chemical activation. Oocyte–cumulus complexes were collected from gonadotropin-treated prepubertal female Wistar rats 14 h after human chorionic gonadotropin (hCG) injection. Cumulus nuclei were injected into ovulated oocytes and then stimulated in the presence of 5 mM SrCl2 for 20 min at various time points (0–3.5 h) after injection. Some of the reconstituted eggs were cultured to observe the pronuclear formation, cleavage, and blastocyst formation. The incidences of eggs forming at least one pronucleus or containing two pronuclei were not significantly different among the periods (82.4–83.5% and 43.4–51.9%, respectively). Nor did the incidences of eggs cleaving (86.7–97.7%) and developing to the blastocyst stage (0–3.5%) differ depending on when, after injection, stimulation began. When some of the reconstituted eggs were observed for cytological morphology 1–1.5 h after injection, 71.7% of the eggs caused premature chromatin condensation, but only 46.2% of them formed two spindles around each of maternal and somatic chromatins. However, the morphology of the somatic spindles differed from that of the spindles, which formed around the oocyte chromatins. Only 7.5% of the eggs contained the normal chromosomal number. In many reconstituted oocytes, before activation, an abnormal spindle formation was observed in the somatic chromatins. In conclusion, these results show that non-enucleated rat oocytes injected with cumulus nuclei can form pronuclei and cleave following chemical activation, whereas blastocyst formation is very limited, probably caused by abnormalities in the spindle formation and distribution of somatic chromatids.
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Neff, M. W., et D. J. Burke. « Random segregation of chromatids at mitosis in Saccharomyces cerevisiae. » Genetics 127, no 3 (1 mars 1991) : 463–73. http://dx.doi.org/10.1093/genetics/127.3.463.
Texte intégralRésumé :
Abstract Previous experiments suggest that mitotic chromosome segregation in some fungi is a nonrandom process in which chromatids of the same replicative age are destined for cosegregation. We have investigated the pattern of chromatid segregation in Saccharomyces cerevisiae by labeling the DNA of a strain auxotrophic for thymidine with 5-bromodeoxyuridine. The fate of DNA strands was followed qualitatively by immunofluorescence microscopy and quantitatively by microphotometry using an anti-5-bromodeoxyuridine monoclonal antibody. Chromatids of the same replicative age were distributed randomly to daughter cells at mitosis. Quantitative measurements showed that the amount of fluorescence in the daughter nuclei derived from parents with hemilabeled chromosomes diminished in intensity by one half. The concentration of 5-bromodeoxyuridine used in the experiments had little effect on the frequency of either homologous or sister chromatid exchanges. We infer that the 5-bromodeoxyuridine was distributed randomly due to mitotic segregation of chromatids and not via sister chromatid exchanges.
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Balicky, Eric M., Matthew W. Endres, Cary Lai et Sharon E. Bickel. « Meiotic Cohesion Requires Accumulation of ORD on Chromosomes before Condensation ». Molecular Biology of the Cell 13, no 11 (novembre 2002) : 3890–900. http://dx.doi.org/10.1091/mbc.e02-06-0332.
Texte intégralRésumé :
Cohesion between sister chromatids is a prerequisite for accurate chromosome segregation during mitosis and meiosis. To allow chromosome condensation during prophase, the connections that hold sister chromatids together must be maintained but still permit extensive chromatin compaction. In Drosophila, null mutations in the orientation disruptor (ord) gene lead to meiotic nondisjunction in males and females because cohesion is absent by the time that sister kinetochores make stable microtubule attachments. We provide evidence that ORD is concentrated within the extrachromosomal domains of the nuclei ofDrosophila primary spermatocytes during early G2, but accumulates on the meiotic chromosomes by mid to late G2. Moreover, using fluorescence in situ hybridization to monitor cohesion directly, we show that cohesion defects first become detectable inord null spermatocytes shortly after the time when wild-type ORD associates with the chromosomes. After condensation, ORD remains bound at the centromeres of wild-type spermatocytes and persists there until centromeric cohesion is released during anaphase II. Our results suggest that association of ORD with meiotic chromosomes during mid to late G2 is required to maintain sister-chromatid cohesion during prophase condensation and that retention of ORD at the centromeres after condensation ensures the maintenance of centromeric cohesion until anaphase II.
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Schubert, Veit, Mateusz Zelkowski, Sonja Klemme et Andreas Houben. « Similar Sister Chromatid Arrangement in Mono- and Holocentric Plant Chromosomes ». Cytogenetic and Genome Research 149, no 3 (2016) : 218–25. http://dx.doi.org/10.1159/000447681.
Texte intégralRésumé :
Due to the X-shape formation at somatic metaphase, the arrangement of the sister chromatids is obvious in monocentric chromosomes. In contrast, the sister chromatids of holocentric chromosomes cannot be distinguished even at mitotic metaphase. To clarify their organization, we differentially labelled the sister chromatids of holocentric Luzula and monocentric rye chromosomes by incorporating the base analogue EdU during replication. Using super-resolution structured illumination microscopy (SIM) and 3D rendering, we found that holocentric sister chromatids attach to each other at their contact surfaces similar to those of monocentrics in prometaphase. We found that sister chromatid exchanges (SCEs) are distributed homogeneously along the whole holocentric chromosomes of Luzula, and that their occurrence is increased compared to monocentric rye chromosomes. The SCE frequency of supernumerary B chromosomes, present additionally to the essential A chromosome complement of rye, does not differ from that of A chromosomes. Based on these results, models of the sister chromatid arrangement in mono- and holocentric plant chromosomes are presented.
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Noel Calir, Martina, Daniela Marisol Ferré, Valeria Ledda et Nora Bibiana Maria Gorla. « Chromosomal aberrations induced by Mitomycin C in canine lymphocytes ». Veterinarski arhiv 93, no 3 (2 août 2023) : 341–50. http://dx.doi.org/10.24099/vet.arhiv.1698.
Texte intégralRésumé :
Chromosomal aberrations comprise an abnormal number of chromosomes as well as changes in the structure of the chromosomes. Aberrations in the structure of chromosomes, such as gaps and breaks in chromatids and chromosomes, acentric fragments, telomeric associations, deletions, early chromatid-separation and large scale effects, such as pulverized metaphases, and sticky metaphases. In this study, the effect of Mitomycin C, a recognized clastogen on human lymphocytes, was assayed in cultures of canine lymphocytes, an animal species that is flourishing in comparative medicine. Blood cultures were performed on samples from a male and a female dog. Cytotoxicity using the mitotic index and genotoxicity testing were performed with 0.25 µg/ml Mitomycin C. The total chromosomal aberrations were significantly higher due to the effect of Mitomycin C (P=0.0247). The number of chromatid breaks nearly quintupled, while pulverized metaphases were found to be six times more frequent, and endoduplicated cells were three times higher than in negative control cultures. The quantitatively most relevant chromosomal aberration was the presence of sticky metaphases, related to adverse effects in chromatin proteins. The potential use of canine lymphocytes for chromosomal aberration assay is emphasized in the evaluation or re-evaluation of the genotoxic in vitro effect of xenobiotics, to evidence chromosomal damage.
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Kateneva, Anna V., Anton A. Konovchenko, Vincent Guacci et Michael E. Dresser. « Recombination protein Tid1p controls resolution of cohesin-dependent linkages in meiosis in Saccharomyces cerevisiae ». Journal of Cell Biology 171, no 2 (17 octobre 2005) : 241–53. http://dx.doi.org/10.1083/jcb.200505020.
Texte intégralRésumé :
Sister chromatid cohesion and interhomologue recombination are coordinated to promote the segregation of homologous chromosomes instead of sister chromatids at the first meiotic division. During meiotic prophase in Saccharomyces cerevisiae, the meiosis-specific cohesin Rec8p localizes along chromosome axes and mediates most of the cohesion. The mitotic cohesin Mcd1p/Scc1p localizes to discrete spots along chromosome arms, and its function is not clear. In cells lacking Tid1p, which is a member of the SWI2/SNF2 family of helicase-like proteins that are involved in chromatin remodeling, Mcd1p and Rec8p persist abnormally through both meiotic divisions, and chromosome segregation fails in the majority of cells. Genetic results indicate that the primary defect in these cells is a failure to resolve Mcd1p-mediated connections. Tid1p interacts with recombination enzymes Dmc1p and Rad51p and has an established role in recombination repair. We propose that Tid1p remodels Mcd1p-mediated cohesion early in meiotic prophase to facilitate interhomologue recombination and the subsequent segregation of homologous chromosomes.
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Eykelenboom, John K., Marek Gierliński, Zuojun Yue, Nadia Hegarat, Hilary Pollard, Tatsuo Fukagawa, Helfrid Hochegger et Tomoyuki U. Tanaka. « Live imaging of marked chromosome regions reveals their dynamic resolution and compaction in mitosis ». Journal of Cell Biology 218, no 5 (11 mars 2019) : 1531–52. http://dx.doi.org/10.1083/jcb.201807125.
Texte intégralRésumé :
When human cells enter mitosis, chromosomes undergo substantial changes in their organization to resolve sister chromatids and compact chromosomes. To comprehend the timing and coordination of these events, we need to evaluate the progression of both sister chromatid resolution and chromosome compaction in one assay. Here we achieved this by analyzing changes in configuration of marked chromosome regions over time, with high spatial and temporal resolution. This assay showed that sister chromatids cycle between nonresolved and partially resolved states with an interval of a few minutes during G2 phase before completing full resolution in prophase. Cohesins and WAPL antagonistically regulate sister chromatid resolution in late G2 and prophase while local enrichment of cohesin on chromosomes prevents precocious sister chromatid resolution. Moreover, our assay allowed quantitative evaluation of condensin II and I activities, which differentially promote sister chromatid resolution and chromosome compaction, respectively. Our assay reveals novel aspects of dynamics in mitotic chromosome resolution and compaction that were previously obscure in global chromosome assays.
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Kotadia, Shaila, Emilie Montembault, William Sullivan et Anne Royou. « Cell elongation is an adaptive response for clearing long chromatid arms from the cleavage plane ». Journal of Cell Biology 199, no 5 (26 novembre 2012) : 745–53. http://dx.doi.org/10.1083/jcb.201208041.
Texte intégralRésumé :
Chromosome segregation must be coordinated with cell cleavage to ensure correct transmission of the genome to daughter cells. Here we identify a novel mechanism by which Drosophila melanogaster neuronal stem cells coordinate sister chromatid segregation with cleavage furrow ingression. Cells adapted to a dramatic increase in chromatid arm length by transiently elongating during anaphase/telophase. The degree of cell elongation correlated with the length of the trailing chromatid arms and was concomitant with a slight increase in spindle length and an enlargement of the zone of cortical myosin distribution. Rho guanine-nucleotide exchange factor (Pebble)–depleted cells failed to elongate during segregation of long chromatids. As a result, Pebble-depleted adult flies exhibited morphological defects likely caused by cell death during development. These studies reveal a novel pathway linking trailing chromatid arms and cortical myosin that ensures the clearance of chromatids from the cleavage plane at the appropriate time during cytokinesis, thus preserving genome integrity.
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Ishak, Muhiddin, Rashidah Baharudin, Isa Mohamed Rose, Ismail Sagap, Luqman Mazlan, Zairul Azwan Mohd Azman, Nadiah Abu, Rahman Jamal, Learn-Han Lee et Nurul Syakima Ab Mutalib. « Genome-Wide Open Chromatin Methylome Profiles in Colorectal Cancer ». Biomolecules 10, no 5 (5 mai 2020) : 719. http://dx.doi.org/10.3390/biom10050719.
Texte intégralRésumé :
The methylome of open chromatins was investigated in colorectal cancer (CRC) to explore cancer-specific methylation and potential biomarkers. Epigenome-wide methylome of open chromatins was studied in colorectal cancer tissues using the Infinium DNA MethylationEPIC assay. Differentially methylated regions were identified using the ChAMP Bioconductor. Our stringent analysis led to the discovery of 2187 significant differentially methylated open chromatins in CRCs. More hypomethylated probes were observed and the trend was similar across all chromosomes. The majority of hyper- and hypomethylated probes in open chromatin were in chromosome 1. Our unsupervised hierarchical clustering analysis showed that 40 significant differentially methylated open chromatins were able to segregate CRC from normal colonic tissues. Receiver operating characteristic analyses from the top 40 probes revealed several significant, highly discriminative, specific and sensitive probes such as OPLAH cg26256223, EYA4 cg01328892, and CCNA1 cg11513637, among others. OPLAH cg26256223 hypermethylation is associated with reduced gene expression in the CRC. This study reports many open chromatin loci with novel differential methylation statuses, some of which with the potential as candidate markers for diagnostic purposes.
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van Schie, Janne J. M., et Job de Lange. « The Interplay of Cohesin and the Replisome at Processive and Stressed DNA Replication Forks ». Cells 10, no 12 (8 décembre 2021) : 3455. http://dx.doi.org/10.3390/cells10123455.
Texte intégralRésumé :
The cohesin complex facilitates faithful chromosome segregation by pairing the sister chromatids after DNA replication until mitosis. In addition, cohesin contributes to proficient and error-free DNA replication. Replisome progression and establishment of sister chromatid cohesion are intimately intertwined processes. Here, we review how the key factors in DNA replication and cohesion establishment cooperate in unperturbed conditions and during DNA replication stress. We discuss the detailed molecular mechanisms of cohesin recruitment and the entrapment of replicated sister chromatids at the replisome, the subsequent stabilization of sister chromatid cohesion via SMC3 acetylation, as well as the role and regulation of cohesin in the response to DNA replication stress.
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Finardi, Alice, Lucia F. Massari et Rosella Visintin. « Anaphase Bridges : Not All Natural Fibers Are Healthy ». Genes 11, no 8 (7 août 2020) : 902. http://dx.doi.org/10.3390/genes11080902.
Texte intégralRésumé :
At each round of cell division, the DNA must be correctly duplicated and distributed between the two daughter cells to maintain genome identity. In order to achieve proper chromosome replication and segregation, sister chromatids must be recognized as such and kept together until their separation. This process of cohesion is mainly achieved through proteinaceous linkages of cohesin complexes, which are loaded on the sister chromatids as they are generated during S phase. Cohesion between sister chromatids must be fully removed at anaphase to allow chromosome segregation. Other (non-proteinaceous) sources of cohesion between sister chromatids consist of DNA linkages or sister chromatid intertwines. DNA linkages are a natural consequence of DNA replication, but must be timely resolved before chromosome segregation to avoid the arising of DNA lesions and genome instability, a hallmark of cancer development. As complete resolution of sister chromatid intertwines only occurs during chromosome segregation, it is not clear whether DNA linkages that persist in mitosis are simply an unwanted leftover or whether they have a functional role. In this review, we provide an overview of DNA linkages between sister chromatids, from their origin to their resolution, and we discuss the consequences of a failure in their detection and processing and speculate on their potential role.
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Oliveira, Raquel A., Paula A. Coelho et Claudio E. Sunkel. « The Condensin I Subunit Barren/CAP-H Is Essential for the Structural Integrity of Centromeric Heterochromatin during Mitosis ». Molecular and Cellular Biology 25, no 20 (15 octobre 2005) : 8971–84. http://dx.doi.org/10.1128/mcb.25.20.8971-8984.2005.
Texte intégralRésumé :
ABSTRACT During cell division, chromatin undergoes structural changes essential to ensure faithful segregation of the genome. Condensins, abundant components of mitotic chromosomes, are known to form two different complexes, condensins I and II. To further examine the role of condensin I in chromosome structure and in particular in centromere organization, we depleted from S2 cells the Drosophila CAP-H homologue Barren, a subunit exclusively associated with condensin I. In the absence of Barren/CAP-H the condensin core subunits DmSMC4/2 still associate with chromatin, while the other condensin I non-structural maintenance of chromosomes family proteins do not. Immunofluorescence and in vivo analysis of Barren/CAP-H-depleted cells showed that mitotic chromosomes are able to condense but fail to resolve sister chromatids. Additionally, Barren/CAP-H-depleted cells show chromosome congression defects that do not appear to be due to abnormal kinetochore-microtubule interaction. Instead, the centromeric and pericentromeric heterochromatin of Barren/CAP-H-depleted chromosomes shows structural problems. After bipolar attachment, the centromeric heterochromatin organized in the absence of Barren/CAP-H cannot withstand the forces exerted by the mitotic spindle and undergoes irreversible distortion. Taken together, our data suggest that the condensin I complex is required not only to promote sister chromatid resolution but also to maintain the structural integrity of centromeric heterochromatin during mitosis.
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Donnellan, Leigh, Clifford Young, Bradley S. Simpson, Varinderpal S. Dhillon, Maurizio Costabile, Peter Hoffmann, Michael Fenech et Permal Deo. « Methylglyoxal Impairs Sister Chromatid Separation in Lymphocytes ». International Journal of Molecular Sciences 23, no 8 (8 avril 2022) : 4139. http://dx.doi.org/10.3390/ijms23084139.
Texte intégralRésumé :
The accurate segregation of sister chromatids is complex, and errors that arise throughout this process can drive chromosomal instability and tumorigenesis. We recently showed that methylglyoxal (MGO), a glycolytic by-product, can cause chromosome missegregation events in lymphocytes. However, the underlying mechanisms of this were not explored. Therefore, in this study, we utilised shotgun proteomics to identify MGO-modified proteins, and label-free quantitation to measure changes in protein abundance following exposure to MGO. We identified numerous mitotic proteins that were modified by MGO, including those involved in the separation and cohesion of sister chromatids. Furthermore, the protein abundance of Securin, an inhibitor of sister chromatid separation, was increased following treatment with MGO. Cytological examination of chromosome spreads showed MGO prevented sister chromatid separation, which was associated with the formation of complex nuclear anomalies. Therefore, results from this study suggest MGO may drive chromosomal instability by preventing sister chromatid separation.
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Andreev L. N., Tsyganok H. A., Soshnicova J. B. et Kozhina A. D. « Investigation and calculation of two-component chromatic aberration compensator ». Optics and Spectroscopy 130, no 8 (2022) : 1045. http://dx.doi.org/10.21883/eos.2022.08.54780.2819-22.
Texte intégralRésumé :
The chromatic aberrations compensator from two hyperchromatic lenses has been investigated. Dependencies of values of chromatic aberrations from parameters of the two-component compensator have been obtained. On the basis of theoretical data, an aberration compensator for high-aperture immersion achromatic microscope lenses has been calculated. Keywords: microscope lens, achromate, chromatic aberration, hyperchromatic lenses, chromatism of magnification - transverse chromatic aberration.
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Miyazaki, W. Y., et T. L. Orr-Weaver. « Sister-chromatid misbehavior in Drosophila ord mutants. » Genetics 132, no 4 (1 décembre 1992) : 1047–61. http://dx.doi.org/10.1093/genetics/132.4.1047.
Texte intégralRésumé :
Abstract In Drosophila males and females mutant for the ord gene, sister chromatids prematurely disjoin in meiosis. We have isolated five new alleles of ord and analyzed them both as homozygotes and in trans to deficiencies for the locus, and we show that ord function is necessary early in meiosis of both sexes. Strong ord alleles result in chromosome nondisjunction in meiosis I that appears to be the consequence of precocious separation of the sister chromatids followed by their random segregation. Cytological analysis in males confirmed that precocious disjunction of the sister chromatids occurs in prometaphase I. This is in contrast to Drosophila mei-S332 mutants, in which precocious sister-chromatid separation also occurs, but not until late in anaphase I. All three of the new female fertile ord alleles reduce recombination, suggesting they affect homolog association as well as sister-chromatid cohesion. In addition to the effect of ord mutations on meiosis, we find that in ord2 mutants chromosome segregation is aberrant in the mitotic divisions that produce the spermatocytes. The strongest ord alleles, ord2 and ord5, appear to cause defects in germline divisions in the female. These alleles are female sterile and produce egg chambers with altered nurse cell number, size, and nuclear morphology. In contrast to the effects of ord mutations on germline mitosis, all of the alleles are fully viable even when in trans to a deficiency, and thus exhibit no essential role in somatic mitosis. The ord gene product may prevent premature sister-chromatid separation by promoting cohesion of the sister chromatids in a structural or regulatory manner.
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Petit, François, Henri Debontride, Michel Lenglet, Gérard Juhel et Didier Verchere. « Contribution of Spectrometric Methods to the Study of the Constituents of Chromating Layers ». Applied Spectroscopy 49, no 2 (février 1995) : 207–10. http://dx.doi.org/10.1366/0003702953963733.
Texte intégralRésumé :
The amorphous constituents of a chromating layer may be defined by the simultaneous use of diffuse reflection spectrometry in the ultraviolet and visible, and of Fourier transform infrared spectrometry. The PO4 group is characterized in the infrared reflection spectrum by bands located near 1070, 1030, and 900 cm−1 for chromium phosphate. The CrO4 group induces bands at 960, 860, and 820 cm−1 for zinc chromate and at about 980, 950, and 860 cm−1 for chromium chromates. The ligandmetal charge transfer bands (LMCT) characteristic of the chromates are situated in the region 3.35 to 4.20 eV. The study of the thermal behavior of chromium phosphate CrPO4 and zinc chromate ZnCrO4 shows that these compounds are stable up to 300°C. Complex chromates of Cr(III) may be observed in the range 150 to 300°C. These analytical data show the contribution of these methods which, used in the reflection mode, are demonstrably the best suited to the analysis of chromating layers on coated steel, of which the primary constituents are chromium phosphate and complex Cr(III) chromates. These results allow the interpretation of the thermal behavior of chromating layers.
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Jin, Hui, Vincent Guacci et Hong-Guo Yu. « Pds5 is required for homologue pairing and inhibits synapsis of sister chromatids during yeast meiosis ». Journal of Cell Biology 186, no 5 (7 septembre 2009) : 713–25. http://dx.doi.org/10.1083/jcb.200810107.
Texte intégralRésumé :
During meiosis, homologues become juxtaposed and synapsed along their entire length. Mutations in the cohesin complex disrupt not only sister chromatid cohesion but also homologue pairing and synaptonemal complex formation. In this study, we report that Pds5, a cohesin-associated protein known to regulate sister chromatid cohesion, is required for homologue pairing and synapsis in budding yeast. Pds5 colocalizes with cohesin along the length of meiotic chromosomes. In the absence of Pds5, the meiotic cohesin subunit Rec8 remains bound to chromosomes with only minor defects in sister chromatid cohesion, but sister chromatids synapse instead of homologues. Double-strand breaks (DSBs) are formed but are not repaired efficiently. In addition, meiotic chromosomes undergo hypercondensation. When the mitotic cohesin subunit Mcd1 is substituted for Rec8 in Pds5-depleted cells, chromosomes still hypercondense, but synapsis of sister chromatids is abolished. These data suggest that Pds5 modulates the Rec8 activity to facilitate chromosome morphological changes required for homologue synapsis, DSB repair, and meiotic chromosome segregation.
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Skibbens, Robert V. « Unzipped and loaded ». Journal of Cell Biology 169, no 6 (13 juin 2005) : 841–46. http://dx.doi.org/10.1083/jcb.200503129.
Texte intégralRésumé :
It is well known that the products of chromosome replication are paired to ensure that the sisters segregate away from each other during mitosis. A key issue is how cells pair sister chromatids but preclude the catastrophic pairing of nonsister chromatids. The identification of both replication factor C and DNA helicases as critical for sister chromatid pairing has brought new insights into this fundamental process.
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Oomen, Marlies E., Adam K. Hedger, Jonathan K. Watts et Job Dekker. « Detecting chromatin interactions between and along sister chromatids with SisterC ». Nature Methods 17, no 10 (23 septembre 2020) : 1002–9. http://dx.doi.org/10.1038/s41592-020-0930-9.
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Tan, Yan Jun, Chang Nan Liu et Yang Zhao. « Detection Methods of Roller Pressure to Design the Chromatism of Dyed Fabrics ». Advanced Materials Research 503-504 (avril 2012) : 633–36. http://dx.doi.org/10.4028/www.scientific.net/amr.503-504.633.
Texte intégralRésumé :
This paper takes CIE1976 L*a*b* chromatism formula as standards, and it takes K/S values and chromatism as characterizations. We design the internal relations and numerical relationships of the fabric chromatism according to the roll’s pressure’s change in pad dyeing, and adjust the padder roller pressure on both sides to eliminate chromatic aberration.
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Severin, Fedor, Anthony A. Hyman et Simonetta Piatti. « Correct spindle elongation at the metaphase/anaphase transition is an APC-dependent event in budding yeast ». Journal of Cell Biology 155, no 5 (26 novembre 2001) : 711–18. http://dx.doi.org/10.1083/jcb.200104096.
Texte intégralRésumé :
At the metaphase to anaphase transition, chromosome segregation is initiated by the splitting of sister chromatids. Subsequently, spindles elongate, separating the sister chromosomes into two sets. Here, we investigate the cell cycle requirements for spindle elongation in budding yeast using mutants affecting sister chromatid cohesion or DNA replication. We show that separation of sister chromatids is not sufficient for proper spindle integrity during elongation. Rather, successful spindle elongation and stability require both sister chromatid separation and anaphase-promoting complex activation. Spindle integrity during elongation is dependent on proteolysis of the securin Pds1 but not on the activity of the separase Esp1. Our data suggest that stabilization of the elongating spindle at the metaphase to anaphase transition involves Pds1-dependent targets other than Esp1.
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Suja, J. A., C. Antonio, A. Debec et J. S. Rufas. « Phosphorylated proteins are involved in sister-chromatid arm cohesion during meiosis I ». Journal of Cell Science 112, no 17 (1 septembre 1999) : 2957–69. http://dx.doi.org/10.1242/jcs.112.17.2957.
Texte intégralRésumé :
Sister-chromatid arm cohesion is lost during the metaphase I/anaphase I transition to allow homologue separation. To obtain needed information on this process we have analysed in grasshopper bivalents the sequential release of arm cohesion in relation to the behaviour of chromatid axes. Results show that sister axes are associated during early metaphase I but separate during late metaphase I leading to a concomitant change of chromosome structure that implies the loss of sister-kinetochore cohesion. Afterwards, homologues initiate their separation asynchronously depending on their size, and number and position of chiasmata. In all bivalents thin chromatin strands at the telomeres appeared as the last point of contact between sister chromatids. Additionally, we have analysed the participation of phosphoproteins recognised by the MPM-2 monoclonal antibody against mitotic phosphoproteins in arm cohesion in bivalents and two different kinds of univalents. Results show the absence of MPM-2 phosphoproteins at the interchromatid domain in mitotic chromosomes and meiotic univalents, but their presence in metaphase I bivalents. These phosphoproteins are lost at the onset of anaphase I. Taken together, these data have prompted us to propose a ‘working’ model for the release of arm cohesion during meiosis I. The model suggests that MPM-2 phosphoproteins may act as cohesive proteins associating sister axes. Their modification, once all bivalents are correctly aligned at the metaphase plate, would trigger a change of chromosome structure and the sequential release of sister-kinetochore, arm, and telomere cohesions.
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Stephens, Andrew D., Julian Haase, Leandra Vicci, Russell M. Taylor et Kerry Bloom. « Cohesin, condensin, and the intramolecular centromere loop together generate the mitotic chromatin spring ». Journal of Cell Biology 193, no 7 (27 juin 2011) : 1167–80. http://dx.doi.org/10.1083/jcb.201103138.
Texte intégralRésumé :
Sister chromatid cohesion provides the mechanistic basis, together with spindle microtubules, for generating tension between bioriented chromosomes in metaphase. Pericentric chromatin forms an intramolecular loop that protrudes bidirectionally from the sister chromatid axis. The centromere lies on the surface of the chromosome at the apex of each loop. The cohesin and condensin structural maintenance of chromosomes (SMC) protein complexes are concentrated within the pericentric chromatin, but whether they contribute to tension-generating mechanisms is not known. To understand how pericentric chromatin is packaged and resists tension, we map the position of cohesin (SMC3), condensin (SMC4), and pericentric LacO arrays within the spindle. Condensin lies proximal to the spindle axis and is responsible for axial compaction of pericentric chromatin. Cohesin is radially displaced from the spindle axis and confines pericentric chromatin. Pericentric cohesin and condensin contribute to spindle length regulation and dynamics in metaphase. Together with the intramolecular centromere loop, these SMC complexes constitute a molecular spring that balances spindle microtubule force in metaphase.
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Chiroli, Elena, Valentina Rossio, Giovanna Lucchini et Simonetta Piatti. « The budding yeast PP2ACdc55 protein phosphatase prevents the onset of anaphase in response to morphogenetic defects ». Journal of Cell Biology 177, no 4 (14 mai 2007) : 599–611. http://dx.doi.org/10.1083/jcb.200609088.
Texte intégralRésumé :
Faithful chromosome transmission requires establishment of sister chromatid cohesion during S phase, followed by its removal at anaphase onset. Sister chromatids are tethered together by cohesin, which is displaced from chromosomes through cleavage of its Mcd1 subunit by the separase protease. Separase is in turn inhibited, up to this moment, by securin. Budding yeast cells respond to morphogenetic defects by a transient arrest in G2 with high securin levels and unseparated chromatids. We show that neither securin elimination nor forced cohesin cleavage is sufficient for anaphase in these conditions, suggesting that other factors contribute to cohesion maintainance in G2. We find that the protein phosphatase PP2A bound to its regulatory subunit Cdc55 plays a key role in this process, uncovering a new function for PP2ACdc55 in controlling a noncanonical pathway of chromatid cohesion removal.
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Cabello, Olga A., Elena Eliseeva, WeiGong He, Hagop Youssoufian, Sharon E. Plon, B. R. Brinkley et John W. Belmont. « Cell Cycle-dependent Expression and Nucleolar Localization of hCAP-H ». Molecular Biology of the Cell 12, no 11 (novembre 2001) : 3527–37. http://dx.doi.org/10.1091/mbc.12.11.3527.
Texte intégralRésumé :
Condensin is a conserved 13S heteropentamer composed of two nonidentical structural maintenance of chromosome (SMC) family proteins, in Xenopus XCAP-C and XCAP-E, and three regulatory subunits, XCAP-D2, XCAP-G, and XCAP-H. Both biochemical and genetic analyses have demonstrated an essential role for the 13S condensin complex in mitotic chromosome condensation. Further, a potential requirement for condensin in completion of chromatid arm separation in early anaphase is demonstrated by the mutational phenotypes of the Drosophila homologues ofXCAP-H, barren and XCAP-C,DmSMC4. In this study we have investigated the expression and subcellular distribution of hCAP-H, the human homolog of XCAP-H, in order to better understand its cellular functions. Transcription of hCAP-H was restricted to proliferating cells with highest expression during the G2 phase of the cell cycle. In contrast, cellular hCAP-H protein levels were constant throughout the cell cycle. hCAP-H was found to be associated with mitotic chromosomes exhibiting a nonuniform but symmetric distribution along sister chromatids. The symmetry of hCAP-H association with sister chromatids suggests that there are sequence-dependent domains of condensin aggregation. During interphase hCAP-H, -C, and -E, have distinct punctate nucleolar localization, suggesting that condensin may associate with and modulate the conformation and function of rDNA. hCAP-H association with condensed chromatin was not observed in the early phase of chromosome condensation when histone H3 phosphorylation has already taken place. This finding is consistent with the hypothesis that histone H3 phosphorylation precedes condensin-mediated condensation.
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Pinkaew, Aeggarut, Tulaya Limpiti et Akraphon Trirat. « Chromatin Detection in Malaria Thick Blood Film Using Automated Image Processing ». Applied Mechanics and Materials 781 (août 2015) : 616–19. http://dx.doi.org/10.4028/www.scientific.net/amm.781.616.
Texte intégralRésumé :
Malaria is a serious global health problem and rapid, accurate diagnosis is required to control the disease. An image processing algorithm to aid the diagnosis of malaria on thick blood films is developed. Morphological and automatic threshold selection techniques are applied on two color components from the HSI color model to identify chromatins of P. Falciparum and P. Vivax malaria species on the images. Chromatins are positively identified with good sensitivities for both species. After identifying the position of chromatins, the algorithm splits the image into small sub-images, each with a chromatin in the center. These small images can subsequently be used by technician to classify malaria species more conveniently.