Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chromosome Segregation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed2004

Cdc14 phosphatase induces rDNA condensation and resolves cohesin-independent cohesion during budding yeast anaphase.

At anaphase onset, the protease separase triggers chromosome segregation by cleaving the chromosomal cohesin complex. Here, we show that cohesin destruction in metaphase is sufficient for segregation of much of the budding yeast genome, but not of the long arm of chromosome XII that contains the rDNA repeats. rDNA in metaphase, unlike most other sequences, remains in an undercondensed and topologically entangled state. Separase, concomitantly with cleaving cohesin, activates the phosphatase Cdc14. We find that Cdc14 exerts two effects on rDNA, both mediated by the condensin complex. Lengthwise condensation of rDNA shortens the chromosome XII arm sufficiently for segregation. This condensation depends on the aurora B kinase complex. Independently of condensation, Cdc14 induces condensin-dependent resolution of cohesin-independent rDNA linkage. Cdc14-dependent sister chromatid resolution at the rDNA could introduce a temporal order to chromosome segregation.

Adenosine Triphosphatases↗
PubMed2006

The FtsK gamma domain directs oriented DNA translocation by interacting with KOPS.

The bacterial septum-located DNA translocase FtsK coordinates circular chromosome segregation with cell division. Rapid translocation of DNA by FtsK is directed by 8-base-pair DNA motifs (KOPS), so that newly replicated termini are brought together at the developing septum, thereby facilitating completion of chromosome segregation. Translocase functions reside in three domains, alpha, beta and gamma. FtsKalphabeta are necessary and sufficient for ATP hydrolysis-dependent DNA translocation, which is modulated by FtsKgamma through its interaction with KOPS. By solving the FtsKgamma structure by NMR, we show that gamma is a winged-helix domain. NMR chemical shift mapping localizes the DNA-binding site on the gamma domain. Mutated proteins with substitutions in the FtsKgamma DNA-recognition helix are impaired in DNA binding and KOPS recognition, yet remain competent in DNA translocation and XerCD-dif site-specific recombination, which facilitates the late stages of chromosome segregation.

Base Sequence↗
PubMed2006

Condensin and Repo-Man-PP1 co-operate in the regulation of chromosome architecture during mitosis.

The reversible condensation of chromosomes during cell division remains a classic problem in cell biology. Condensation requires the condensin complex in certain experimental systems, but not in many others. Anaphase chromosome segregation almost always fails in condensin-depleted cells, leading to the formation of prominent chromatin bridges and cytokinesis failure. Here, live-cell analysis of chicken DT40 cells bearing a conditional knockout of condensin subunit SMC2 revealed that condensin-depleted chromosomes abruptly lose their compact architecture during anaphase and form massive chromatin bridges. The compact chromosome structure can be preserved and anaphase chromosome segregation rescued by preventing the targeting subunit Repo-Man from recruiting protein phosphatase 1 (PP1) to chromatin at anaphase onset. This study identifies an activity critical for mitotic chromosome structure that is inactivated by Repo-Man-PP1 during anaphase. This activity, provisionally termed 'regulator of chromosome architecture' (RCA), cooperates with condensin to preserve the characteristic chromosome architecture during mitosis.

Adenosine Triphosphatases↗
PubMed2004

M chromosome of the wild silkworm, Bombyx mandarina (n = 27), corresponds to two chromosomes in the domesticated silkworm, Bombyx mori (n = 28).

Chromosomes of Bombyx mori (n = 28) and of Bombyx mandarina (n = 27) were studied cytogenetically to resolve the origin of the large M chromosome in the Japaneses type of B. mandarina. In the F1 progeny from the reciprocal cross between B. mandarina and B. mori, the mitotic chromosome number was 2n = 55, and a chromosome configuration of 26 bivalents plus 1 trivalent was observed at metaphase I of germ cells. The trivalent chromosome consisted of the M chromosome from B. mandarina and two chromosomes from B. mori. When males of B. mori were mated to the F1 females, nuclei with two types of chromosome number (2n = 55 and 2n = 56) and two sets of chromosome pairs (26 bivalents plus 1 trivalent versus 28 bivalents) were observed in the metaphase I stage. Linkage analysis showed that the 14th chromosome of B. mori was involved in these two types of chromosome segregation. This result indicates that the M chromosome in B. mandarina arose from a fusion between a chromosome corresponding to the 14th linkage group and another, yet unidentified linkage group.

Animals↗
PubMed2005

Bacterial DNA segregation by the actin-like MreB protein.

Faithful chromosome segregation is vital to all organisms. Eukaryotic cells use the tubulin-based cytoskeleton to segregate their chromosomes during mitosis. A handful of papers have provided convincing evidence that, in bacteria, this task is accomplished by the actin homolog MreB. In particular, a recent study by Gitai et al. demonstrates that MreB specifically binds to and segregates the replication origin of the bacterial chromosome.

Actins↗
PubMedDate not supplied

The DASH complex component Ask1 is a cell cycle-regulated Cdk substrate in Saccharomyces cerevisiae.

The proper timing and fidelity of cell cycle transitions is critical for the survival of organisms. Cyclin-dependent kinases orchestrate many cell cycle transitions in eukaryotes including S phase entry and mitosis. Accurate chromosome segregation during mitosis is one of the key events regulated by the cell cycle and many proteins function together to ensure the fidelity of this process. In S. cerevisiae, the DASH complex is essential for chromosome segregation. The DASH complex binds to microtubules and kinetochores and regulates their association. Here we report that Askl, one component of DASH, is phosphorylated during the cell cycle. This phosphorylation is dependent on Cdks in vivo, and in vitro Cdc28 can phosphorylate Askl. We identify two Cdk phosphorylation sites in Askl and find that the phosphorylation of Askl is important for its full activity in vivo. Thus, the DASH complex is directly regulated by cyclin-dependent kinases to facilitate chromosome segregation.

Amino Acid Sequence↗
PubMed2005

Inactivation of the pre-mRNA cleavage and polyadenylation factor Pfs2 in fission yeast causes lethal cell cycle defects.

Faithful chromosome segregation is fundamentally important for the maintenance of genome integrity and ploidy. By isolating conditional mutants defective in chromosome segregation in the fission yeast Schizosaccharomyces pombe, we identified a role for the essential gene pfs2 in chromosome dynamics. In the absence of functional Pfs2, chromosomal attachment to the mitotic spindle was defective, with consequent chromosome missegregation. Under these circumstances, multiple intracellular foci of spindle checkpoint proteins Bub1 and Mad2 were seen, and deletion of bub1 exacerbated the mitotic defects and the loss of cell viability that resulted from the loss of pfs2 function. Progression from G1 into S phase following release from nitrogen starvation also required pfs2+ function. The product of the orthologous Saccharomyces cerevisiae gene PFS2 is a component of a multiprotein complex required for 3'-end cleavage and polyadenylation of pre-mRNAs and, in keeping with the conservation of this essential function, an S. pombe pfs2 mutant was defective in mRNA 3'-end processing. Mutations in pfs2 were suppressed by overexpression of the putative mRNA 3'-end cleavage factor Cft1. These data suggest unexpected links between mRNA 3'-end processing and chromosome replication and segregation.

Carrier Proteins↗
PubMed2005

The yeast APC/C subunit Mnd2 prevents premature sister chromatid separation triggered by the meiosis-specific APC/C-Ama1.

Cohesion established between sister chromatids during pre-meiotic DNA replication mediates two rounds of chromosome segregation. The first division is preceded by an extended prophase wherein homologous chromosomes undergo recombination. The persistence of cohesion during prophase is essential for recombination and both meiotic divisions. Here we show that Mnd2, a subunit of the anaphase-promoting complex (APC/C) from budding yeast, is essential to prevent premature destruction of cohesion in meiosis. During S- and prophase, Mnd2 prevents activation of the APC/C by a meiosis-specific activator called Ama1. In cells lacking Mnd2 the APC/C-Ama1 enzyme triggers degradation of Pds1, which causes premature sister chromatid separation due to unrestrained separase activity. In vitro, Mnd2 inhibits ubiquitination of Pds1 by APC/C-Ama1 but not by other APC/C holo-enzymes. We conclude that chromosome segregation in meiosis depends on the selective inhibition of a meiosis-specific form of the APC/C.

Anaphase↗
PubMed2004

Linked for life: temporal and spatial coordination of late mitotic events.

Establishing the temporal order of mitotic events is critical to ensure that each daughter cell receives a complete DNA complement. The spatial co-ordination of the cytokinetic ring site with the axis of chromosome segregation is likewise crucial. Recent studies in fungi indicate that regulators of chromosome segregation also participate in promoting mitotic exit and that the proteins that initiate mitotic exit, in turn, additionally regulate cytokinesis. These findings suggest that late mitotic events are coupled by employing one pathway to control multiple events. The regulatory mechanisms that ensure the spatial co-ordination of the mitotic spindle apparatus with the division site have also been elucidated recently in the asymmetrically dividing budding yeast. Interestingly, the spatial co-ordination of late mitotic events seems also to be important in higher eukaryotes.

Animals↗
PubMed1996

An extragenic suppressor of the mitosis-defective bimD6 mutation of Aspergillus nidulans codes for a chromosome scaffold protein.

We previously identified a gene, bimD, that functions in chromosome segregation and contains sequences suggesting that it may be a DNA-binding protein. Two conditionally lethal mutations in bimD arrest with aberrant mitotic spindles at restrictive temperature. These spindles have one-third the normal number of microtubules, and the chromosomes never attach to the remaining microtubules. For this reason, we hypothesized that BIMD functioned in chromosome segregation, possibly as a component of the kinetochore. To identify other components that function with bimD, we conducted a screen for extragenic suppressors of the bimD5 and bimD6 mutations. We have isolated seven cold-sensitive extragenic suppressors of bimD6 heat sensitivity that represent three or possibly four separate sud genes. We have cloned one of the suppressor genes by complementation of the cold-sensitive phenotype of the sudA3 mutation. SUDA belongs to the DA-box protein family. DA-box proteins have been shown to function in chromosome structure and segregation. Thus bimD and the sud genes cooperatively function in chromosome segregation in Aspergillus nidulans.

Alleles↗
PubMed2005

A mitotic septin scaffold required for Mammalian chromosome congression and segregation.

Coordination of cytokinesis with chromosome congression and segregation is critical for proper cell division, but the mechanism is unknown. Here, septins, a conserved family of polymerizing guanosine triphosphate-binding proteins, localized to the metaphase plate during mitosis. Septin depletion resulted in chromosome loss from the metaphase plate, lack of chromosome segregation and spindle elongation, and incomplete cytokinesis upon delayed mitotic exit. These defects correlated with loss of the mitotic motor and the checkpoint regulator centromere-associated protein E (CENP-E) from the kinetochores of congressing chromosomes. Mammalian septins may thus form a mitotic scaffold for CENP-E and other effectors to coordinate cytokinesis with chromosome congression and segregation.

Animals↗
PubMed1993

Chromosomal rearrangement segregating with adrenoleukodystrophy: a molecular analysis.

The relationship between X chromosome-linked adrenoleukodystrophy and the red/green color pigment gene cluster on Xq28 was investigated in a large kindred. The DNA in a hemizygous male showed altered restriction fragment sizes compatible with at least a deletion extending from the 5' end of the color pigment genes. Segregation analysis using a DNA probe within the color pigment gene cluster showed significant linkage with adrenoleukodystrophy (logarithm of odds score of 3.19 at theta = 0.0). These data demonstrate linkage, rather than association, between a unique molecular rearrangement in the color pigment gene cluster and adrenoleukodystrophy. The DNA changes in this region are thus likely to be helpful for determining the location and identity of the responsible gene.

Adrenoleukodystrophy↗
PubMed2003

Regulation of chromosome condensation and segregation.

Regulated and controlled chromosome condensation and segregation is essential for the transmission of genetic information from one generation to the next. A myriad of techniques has been utilized over the last few decades to identify proteins required for the organized compaction of the massive length of a cell's DNA. A full understanding of the components and processes involved relies on further work, exploiting biochemical, genetic, cytological, and proteomics approaches to complete the picture of how a cell packages and partitions its genome during the cell cycle.

Animals↗
PubMed2001

The teflon gene is required for maintenance of autosomal homolog pairing at meiosis I in male Drosophila melanogaster.

In recombination-proficient organisms, chiasmata appear to mediate associations between homologs at metaphase of meiosis I. It is less clear how homolog associations are maintained in organisms that lack recombination, such as male Drosophila. In lieu of chiasmata and synaptonemal complexes, there must be molecules that balance poleward forces exerted across homologous centromeres. Here we describe the genetic and cytological characterization of four EMS-induced mutations in teflon (tef), a gene involved in this process in Drosophila melanogaster. All four alleles are male specific and cause meiosis I-specific nondisjunction of the autosomes. They do not measurably perturb sex chromosome segregation, suggesting that there are differences in the genetic control of autosome and sex chromosome segregation in males. Meiotic transmission of univalent chromosomes is unaffected in tef mutants, implicating the tef product in a pairing-dependent process. The segregation of translocations between sex chromosomes and autosomes is altered in tef mutants in a manner that supports this hypothesis. Consistent with these genetic observations, cytological examination of meiotic chromosomes suggests a role of tef in regulating or mediating pairing of autosomal bivalents at meiosis I. We discuss implications of this finding in regard to the evolution of heteromorphic sex chromosomes and the mechanisms that ensure chromosome disjunction in the absence of recombination.

Alleles↗
PubMed2004

Spindles, mitochondria and redox potential in ageing oocytes.

Studies of human oocytes obtained from women of advanced reproductive age revealed that spindles are frequently aberrant, with chromosomes sometimes failing to align properly at the equator during meiosis I and II. Chromosomal analyses of donated and spare human oocytes and cytogenetic and molecular studies on the origin of trisomies collectively suggest that errors in chromosome segregation during oogenesis increase with advancing maternal age and as the menopause approaches. Disturbances in the fidelity of chromosome segregation, especially at anaphase I, leading to aneuploidy are prime causes of reduced developmental competence of embryos in assisted reproduction, as well as being responsible for the genesis of genetic disease. This review provides an overview of spindle formation and chromosome behaviour in mammalian oocytes. Evidence of a link between abnormal mitochondrial function in oocytes and somatic follicular cells, and finally disturbances in chromosome cohesion and segregation, and cell cycle control in aged mammalian oocytes, are also discussed.

Aneuploidy↗
PubMed1974

Oncornavirus expression in human x mouse hybrid cells segregating mouse chromosomes.

Human x mouse hybrid clones obtained by fusing transformed human (VA2) cells with embryonic mouse brain cells were tested for their ability to spontaneously express type C virus particles. It had been previously shown that these hybrid cells preferentially retained human chromosomes while mouse chromosomes were lost. The culture fluid from one cell line was found to contain type C particle markers in abundance, and typical budding C particles were observed in the cells by electron microscopy. In contrast, no particle markers were detected in the culture fluid from parental cells and several other hybrid cell lines. Subclones of the virus-positive cell line continued to lose mouse chromosomes and were found to vary more than 100-fold in their culture fluid DNA polymerase activity. The hybrid cell viruses, termed HMV1, banded in a sucrose gradient between 1.14 and 1.16 g/ml, possessed viral group-specific antigens, and exhibited B-tropic host range for replication in mouse embryo cells, but did not replicate in human cells when directly applied. The virus did not transform mouse cells but was able to rescue the defective murine sarcoma virus from sarcoma-positive, helper-virus-negative cells. Activity of the DNA polymerase associated with HMV1 was similar to the activity of Rauscher murine leukemia virus (MuLV) DNA polymerase in its preference for poly(rA) over poly(dA) as a template, use of endogenous template, detergent requirement, and inhibition by antiserum directed against MuLV.DNA polymerase. The results suggest that human x mouse hybrid cells segregating mouse chromosomes can spontaneously express endogenous type C viruses and that such hybrid cell lines may be used for the isolation of latent mammalian oncornaviruses and analysis of viral gene regulation.

Animals↗
PubMed2003

ago1 and dcr1, two core components of the RNA interference pathway, functionally diverge from rdp1 in regulating cell cycle events in Schizosaccharomyces pombe.

In the fission yeast Schizosaccharomyces pombe, three genes that function in the RNA interference (RNAi) pathway, ago1+, dcr1+, and rdp1+, have recently been shown to be important for timely formation of heterochromatin and accurate chromosome segregation. In the present study, we present evidence that null mutants for ago1+ and dcr1+ but not rdp1+, exhibit abnormal cytokinesis, cell cycle arrest deficiencies, and mating defects. Subsequent analyses showed that ago1+ and dcr1+ are required for regulated hyperphosphorylation of Cdc2 when encountering genotoxic insults. Because rdp1+ is dispensable for this process, the functions of ago1+ and dcr1+ in this pathway are presumably independent of their roles in RNAi-mediated heterochromatin formation and chromosome segregation. This was further supported by the finding that ago1+ is a multicopy suppressor of the S-M checkpoint deficiency and cytokinesis defects associated with loss of Dcr1 function, but not for the chromosome segregation defects of this mutant. Accordingly, we conclude that Dcr1-dependent production of small interfering RNAs is not required for enactment and/or maintenance of certain cell cycle checkpoints and that Ago1 and Dcr1 functionally diverge from Rdp1 to control cell cycle events in fission yeast. Finally, exogenous expression of hGERp95/EIF2C2/hAgo2, a human Ago1 homolog implicated in posttranscriptional gene silencing, compensated for the loss of ago1+ function in S. pombe. This suggests that PPD proteins may also be important for regulation of cell cycle events in higher eukaryotes.

Adenosine Triphosphatases↗
PubMed1985

The expression of human glycerol-3-phosphate dehydrogenase in human/rodent somatic-cell hybrids.

Our previous studies using rodent/human somatic-cell hybrids suggested that the expression of human mitochondrial glycerol-3-phosphate dehydrogenase (GPDM) is dependent on the presence of human mitochondria. This has now been tested directly by analysis of GPDM activity in a series of nine hybrid-cell lines, four segregating human chromosomes and five losing rodent chromosomes (reverse segregants). The chromosome composition of the hybrids was deduced from analysis of biochemical markers and examination of G- and G11-banded metaphase spreads and the mitochondrial content was determined by Southern blot analysis, using cloned mouse and human mtDNA sequences as probes. We found that the mtDNA species present in these hybrids correlated exactly with the pattern of chromosome segregation such that the conventional hybrids contained rodent mtDNA and the reverse segregants human mtDNA. However, the pattern of GPDM expression was not directly correlated with the species of chromosomes or mitochondria present: all the hybrids showed strong rodent GPDM activity and two from each class of hybrid also showed human GPDM activity but the other hybrids were negative for human GPDM. We conclude that rodent GPDM readily integrates into human mitochondria, that the expression of rodent GPDM is not dependent on the presence of rodent mitochondria, and that GPDM is not coded by mtDNA. Human GPDM either is not capable of being inserted into the rodent mitochondrial membrane or is regulated in some way in the hybrid cells by an unidentified rodent factor.

Animals↗