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Arbel‐Eden A, Simchen G. Elevated Mutagenicity in Meiosis and Its Mechanism. Bioessays 2019; 41:e1800235. [DOI: 10.1002/bies.201800235] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 01/31/2019] [Indexed: 12/25/2022]
Affiliation(s)
| | - Giora Simchen
- Department of GeneticsThe Hebrew University of JerusalemJerusalem 91904 Israel
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2
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Börner GV, Cha RS. Analysis of Recombination and Chromosome Structure during Yeast Meiosis. Cold Spring Harb Protoc 2015; 2015:970-4. [PMID: 26527771 DOI: 10.1101/pdb.top077636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Meiosis is a diploid-specific differentiation program that consists of a single round of genome duplication followed by two rounds of chromosome segregation. These events result in halving of the genetic complement, which is a requirement for formation of haploid reproductive cells (i.e., spores in yeast and gametes in animals and plants). During meiosis I, homologous maternal and paternal chromosomes (homologs) pair and separate, whereas sister chromatids remain connected at the centromeres and separate during the second meiotic division. In most organisms, accurate homolog disjunction requires crossovers, which are formed as products of meiotic recombination. For the past two decades, studies of yeast meiosis have provided invaluable insights into evolutionarily conserved mechanisms of meiosis.
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Affiliation(s)
- G Valentin Börner
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological and Environmental Sciences, Cleveland State University, 2121 Euclid Avenue, Cleveland, Ohio 44115-2214
| | - Rita S Cha
- North West Cancer Research Institute, School of Medical Sciences, Bangor University, Bangor LL57 2UW, United Kingdom
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Dynamics of DNA replication during premeiosis and early meiosis in wheat. PLoS One 2014; 9:e107714. [PMID: 25275307 PMCID: PMC4183481 DOI: 10.1371/journal.pone.0107714] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 08/21/2014] [Indexed: 11/19/2022] Open
Abstract
Meiosis is a specialised cell division that involves chromosome replication, two rounds of chromosome segregation and results in the formation of the gametes. Meiotic DNA replication generally precedes chromosome pairing, recombination and synapsis in sexually developing eukaryotes. In this work, replication has been studied during premeiosis and early meiosis in wheat using flow cytometry, which has allowed the quantification of the amount of DNA in wheat anther in each phase of the cell cycle during premeiosis and each stage of early meiosis. Flow cytometry has been revealed as a suitable and user-friendly tool to detect and quantify DNA replication during early meiosis in wheat. Chromosome replication was detected in wheat during premeiosis and early meiosis until the stage of pachytene, when chromosomes are associated in pairs to further recombine and correctly segregate in the gametes. In addition, the effect of the Ph1 locus, which controls chromosome pairing and affects replication in wheat, was also studied by flow cytometry. Here we showed that the Ph1 locus plays an important role on the length of meiotic DNA replication in wheat, particularly affecting the rate of replication during early meiosis in wheat.
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Kerr GW, Sarkar S, Arumugam P. How to halve ploidy: lessons from budding yeast meiosis. Cell Mol Life Sci 2012; 69:3037-51. [PMID: 22481439 PMCID: PMC11114884 DOI: 10.1007/s00018-012-0974-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 03/09/2012] [Accepted: 03/13/2012] [Indexed: 11/26/2022]
Abstract
Maintenance of ploidy in sexually reproducing organisms requires a specialized form of cell division called meiosis that generates genetically diverse haploid gametes from diploid germ cells. Meiotic cells halve their ploidy by undergoing two rounds of nuclear division (meiosis I and II) after a single round of DNA replication. Research in Saccharomyces cerevisiae (budding yeast) has shown that four major deviations from the mitotic cell cycle during meiosis are essential for halving ploidy. The deviations are (1) formation of a link between homologous chromosomes by crossover, (2) monopolar attachment of sister kinetochores during meiosis I, (3) protection of centromeric cohesion during meiosis I, and (4) suppression of DNA replication following exit from meiosis I. In this review we present the current understanding of the above four processes in budding yeast and examine the possible conservation of molecular mechanisms from yeast to humans.
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Affiliation(s)
- Gary William Kerr
- School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK.
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Blitzblau HG, Chan CS, Hochwagen A, Bell SP. Separation of DNA replication from the assembly of break-competent meiotic chromosomes. PLoS Genet 2012; 8:e1002643. [PMID: 22615576 PMCID: PMC3355065 DOI: 10.1371/journal.pgen.1002643] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 02/17/2012] [Indexed: 01/10/2023] Open
Abstract
The meiotic cell division reduces the chromosome number from diploid to haploid to form gametes for sexual reproduction. Although much progress has been made in understanding meiotic recombination and the two meiotic divisions, the processes leading up to recombination, including the prolonged pre-meiotic S phase (meiS) and the assembly of meiotic chromosome axes, remain poorly defined. We have used genome-wide approaches in Saccharomyces cerevisiae to measure the kinetics of pre-meiotic DNA replication and to investigate the interdependencies between replication and axis formation. We found that replication initiation was delayed for a large number of origins in meiS compared to mitosis and that meiotic cells were far more sensitive to replication inhibition, most likely due to the starvation conditions required for meiotic induction. Moreover, replication initiation was delayed even in the absence of chromosome axes, indicating replication timing is independent of the process of axis assembly. Finally, we found that cells were able to install axis components and initiate recombination on unreplicated DNA. Thus, although pre-meiotic DNA replication and meiotic chromosome axis formation occur concurrently, they are not strictly coupled. The functional separation of these processes reveals a modular method of building meiotic chromosomes and predicts that any crosstalk between these modules must occur through superimposed regulatory mechanisms.
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Affiliation(s)
- Hannah G. Blitzblau
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts, United States of America
| | - Clara S. Chan
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Andreas Hochwagen
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, Massachusetts, United States of America
- Department of Biology, New York University, New York, New York, United States of America
| | - Stephen P. Bell
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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7
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Raghuraman MK, Brewer BJ. Molecular analysis of the replication program in unicellular model organisms. Chromosome Res 2010; 18:19-34. [PMID: 20012185 DOI: 10.1007/s10577-009-9099-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Eukaryotes have long been reported to show temporal programs of replication, different portions of the genome being replicated at different times in S phase, with the added possibility of developmentally regulated changes in this pattern depending on species and cell type. Unicellular model organisms, primarily the budding yeast Saccharomyces cerevisiae, have been central to our current understanding of the mechanisms underlying the regulation of replication origins and the temporal program of replication in particular. But what exactly is a temporal program of replication, and how might it arise? In this article, we explore this question, drawing again on the wealth of experimental information in unicellular model organisms.
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Affiliation(s)
- M K Raghuraman
- Department of Genome Sciences, University of Washington, Box 355065, Seattle, WA, 98133, USA.
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8
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Davis GE, Lowell WE. Photons and evolution: quantum mechanical processes modulate sexual differentiation. Med Hypotheses 2009; 73:296-301. [PMID: 19409720 DOI: 10.1016/j.mehy.2009.03.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 03/20/2009] [Accepted: 03/21/2009] [Indexed: 12/01/2022]
Abstract
This paper will show that the fractional difference in the human gender ratio (GR) between the GR(at death) for those born in solar cycle peak years (maxima) and the GR(at death) in those born in solar cycle non-peak years (minima), e.g., 0.023, divided by Pi, yields a reasonable approximation of the quantum mechanical constant, alpha, or the fine structure constant (FSC) approximately 0.007297... or approximately 1/137. This finding is based on a sample of approximately 50 million cases using common, readily available demographic data, e.g., state of birth, birth date, death date, and gender. Physicists Nair, Geim et al. had found precisely the same fractional difference, 0.023, in the absorption of white light (sunlight) by a single-atom thick layer of graphene, a carbon skeleton resembling chicken wire fencing. This absorption fraction, when divided by Pi, yielded the FSC and was the first time this constant could "so directly be assessed practically by the naked eye". As the GR is a reflection of sexual differentiation, this paper reveals that a quantum mechanical process, as manifested by the FSC, is playing a role in the primordial process of replication, a necessary requirement of life. Successful replication is the primary engine driving evolution, which at a biochemical level, is a quantum mechanical process dependent upon photonic energy from the Sun. We propose that a quantum-mechanical, photon-driven chemical evolution preceded natural selection in biology and the mechanisms of mitosis and meiosis are manifestations of this chemical evolution in ancient seas over 3 billion years ago. Evolutionary processes became extant first in self-replicating molecules forced to adapt to high energy photons, mostly likely in the ultraviolet spectrum. These events led to evolution by natural selection as complex mixing of genetic material within species creating the variety needed to match changing environments reflecting the same process initiated at the dawn of life. Both evolutionary mechanisms coexist and are interactive. The periodic energy of solar maxima is likely modulating the human genome from maternal integument to an embryo in utero with non-local mechanisms intrinsic to quantum mechanics.
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Affiliation(s)
- George E Davis
- Psybernetics Inc. (Research Group), 28 Eastern Avenue, Augusta, ME 04330, USA.
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Necsulea A, Guillet C, Cadoret JC, Prioleau MN, Duret L. The relationship between DNA replication and human genome organization. Mol Biol Evol 2009; 26:729-41. [PMID: 19126867 DOI: 10.1093/molbev/msn303] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Assessment of the impact of DNA replication on genome architecture in Eukaryotes has long been hampered by the scarcity of experimental data. Recent work, relying on computational predictions of origins of replication, suggested that replication might be a major determinant of gene organization in human (Huvet et al. 2007. Human gene organization driven by the coordination of replication and transcription. Genome Res. 17:1278-1285). Here, we address this question by analyzing the first large-scale data set of experimentally determined origins of replication in human: 283 origins identified in HeLa cells, in 1% of the genome covered by ENCODE regions (Cadoret et al. 2008. Genome-wide studies highlight indirect links between human replication origins and gene regulation. Proc Natl Acad Sci USA. 105:15837-15842). We show that origins of replication are not randomly distributed as they display significant overlap with promoter regions and CpG islands. The hypothesis of a selective pressure to avoid frontal collisions between replication and transcription polymerases is not supported by experimental data as we find no evidence for gene orientation bias in the proximity of origins of replication. The lack of a significant orientation bias remains manifest even when considering only genes expressed at a high rate, or in a wide number of tissues, and is not affected by the regional replication timing. Gene expression breadth does not appear to be correlated with the distance from the origins of replication. We conclude that the impact of DNA replication on human genome organization is considerably weaker than previously proposed.
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Abstract
Eukaryotic DNA replication is regulated to ensure all chromosomes replicate once and only once per cell cycle. Replication begins at many origins scattered along each chromosome. Except for budding yeast, origins are not defined DNA sequences and probably are inherited by epigenetic mechanisms. Initiation at origins occurs throughout the S phase according to a temporal program that is important in regulating gene expression during development. Most replication proteins are conserved in evolution in eukaryotes and archaea, but not in bacteria. However, the mechanism of initiation is conserved and consists of origin recognition, assembly of prereplication (pre-RC) initiative complexes, helicase activation, and replisome loading. Cell cycle regulation by protein phosphorylation ensures that pre-RC assembly can only occur in G1 phase, whereas helicase activation and loading can only occur in S phase. Checkpoint regulation maintains high fidelity by stabilizing replication forks and preventing cell cycle progression during replication stress or damage.
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Affiliation(s)
- R A Sclafani
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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Apoptosis in mouse fetal and neonatal oocytes during meiotic prophase one. BMC DEVELOPMENTAL BIOLOGY 2007; 7:87. [PMID: 17650311 PMCID: PMC1965470 DOI: 10.1186/1471-213x-7-87] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Accepted: 07/24/2007] [Indexed: 01/13/2023]
Abstract
Background The vast majority of oocytes formed in the fetal ovary do not survive beyond birth. Possible reasons for their loss include the elimination of non-viable genetic constitutions arising through meiosis, however, the precise relationship between meiotic stages and prenatal apoptosis of oocytes remains elusive. We studied oocytes in mouse fetal and neonatal ovaries, 14.5–21 days post coitum, to examine the relationship between oocyte development and programmed cell death during meiotic prophase I. Results Microspreads of fetal and neonatal ovarian cells underwent immunocytochemistry for meiosis- and apoptosis-related markers. COR-1 (meiosis-specific) highlighted axial elements of the synaptonemal complex and allowed definitive identification of the stages of meiotic prophase I. Labelling for cleaved poly-(ADP-ribose) polymerase (PARP-1), an inactivated DNA repair protein, indicated apoptosis. The same oocytes were then labelled for DNA double strand breaks (DSBs) using TUNEL. 1960 oocytes produced analysable results. Oocytes at all stages of meiotic prophase I stained for cleaved PARP-1 and/or TUNEL, or neither. Oocytes with fragmented (19.8%) or compressed (21.2%) axial elements showed slight but significant differences in staining for cleaved PARP-1 and TUNEL to those with intact elements. However, fragmentation of axial elements alone was not a good indicator of cell demise. Cleaved PARP-1 and TUNEL staining were not necessarily coincident, showing that TUNEL is not a reliable marker of apoptosis in oocytes. Conclusion Our data indicate that apoptosis can occur throughout meiotic prophase I in mouse fetal and early postnatal oocytes, with greatest incidence at the diplotene stage. Careful selection of appropriate markers for oocyte apoptosis is essential.
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Jaramillo-Lambert A, Ellefson M, Villeneuve AM, Engebrecht J. Differential timing of S phases, X chromosome replication, and meiotic prophase in the C. elegans germ line. Dev Biol 2007; 308:206-21. [PMID: 17599823 DOI: 10.1016/j.ydbio.2007.05.019] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Revised: 04/02/2007] [Accepted: 05/18/2007] [Indexed: 12/30/2022]
Abstract
The replication of chromosomes in meiosis is an important first step for subsequent chromosomal interactions that promote accurate disjunction in the first of two segregation events to generate haploid gametes. We have developed an assay to monitor DNA replication in vivo in mitotic and meiotic germline nuclei of the nematode Caenorhabditis elegans. Using mutants that affect the mitosis/meiosis switch, we show that meiotic S phase is at least twice as long as mitotic S phase in C. elegans germ cell nuclei. Furthermore, our assay reveals that different regions of the genome replicate at different times, with the heterochromatic-like X chromosomes replicating at a distinct time from the autosomes. Finally, we have exploited S-phase labeling to monitor the timing of progression through meiotic prophase. Meiotic prophase for oocyte production in hermaphrodites lasts 54-60 h. Further, we find that the duration of the pachytene sub-stage is modulated by the presence of sperm. On the other hand, meiotic prophase for sperm production in males is completed by 20-24 h. Possible sources for the sex-specific differences in meiotic prophase kinetics are discussed.
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Affiliation(s)
- Aimee Jaramillo-Lambert
- Section of Molecular and Cellular Biology, Genetics Graduate Group, University of California, Davis, CA 95616, USA
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Heichinger C, Penkett CJ, Bähler J, Nurse P. Genome-wide characterization of fission yeast DNA replication origins. EMBO J 2006; 25:5171-9. [PMID: 17053780 PMCID: PMC1630417 DOI: 10.1038/sj.emboj.7601390] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 09/21/2006] [Indexed: 11/09/2022] Open
Abstract
Eukaryotic DNA replication is initiated from multiple origins of replication, but little is known about the global regulation of origins throughout the genome or in different types of cell cycles. Here, we identify 401 strong origins and 503 putative weaker origins spaced in total every 14 kb throughout the genome of the fission yeast Schizosaccharomyces pombe. The same origins are used during premeiotic and mitotic S-phases. We found that few origins fire late in mitotic S-phase and that activating the Rad3 dependent S-phase checkpoint by inhibiting DNA replication had little effect on which origins were fired. A genome-wide analysis of eukaryotic origin efficiencies showed that efficiency was variable, with large chromosomal domains enriched for efficient or inefficient origins. Average efficiency is twice as high during mitosis compared with meiosis, which can account for their different S-phase lengths. We conclude that there is a continuum of origin efficiency and that there is differential origin activity in the mitotic and meiotic cell cycles.
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Affiliation(s)
- Christian Heichinger
- Laboratory of Yeast Genetics and Cell Biology, The Rockefeller University, New York, NY 10021, USA.
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Abstract
Initiation of DNA replication is a highly regulated process in all organisms. Proteins that are required to recruit DNA polymerase - initiator proteins - are often used to regulate the timing or frequency of initiation in the cell cycle by limiting either their own synthesis or availability. Studies of the Escherichia coli chromosome and of bacterial plasmids with iterated initiator binding sites (iterons) have revealed that, in addition to initiator limitation, replication origin inactivation is used to prevent replication that is untimely or excessive. Our recent studies of plasmid P1 revealed that this additional mode of control becomes a requirement when initiator availability is limited only by autoregulation. Thus, although initiator limitation appears to be a well-conserved and central mode of replication control, optimal replication might require additional control mechanisms. This review gives examples of how the multiple mechanisms can act synergistically, antagonistically or be partially redundant to guarantee low frequency events. The lessons learned are likely to help understand many other regulatory systems in the bacterial cell.
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Affiliation(s)
- Johan Paulsson
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
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Valentin G, Schwob E, Della Seta F. Dual role of the Cdc7-regulatory protein Dbf4 during yeast meiosis. J Biol Chem 2005; 281:2828-34. [PMID: 16319063 DOI: 10.1074/jbc.m510626200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Dbf4-dependent Cdc7 kinase (DDK) is essential for chromosome duplication in all eukaryotes, but was proposed to be dispensable for yeast pre-meiotic DNA replication. This discrepancy led us to investigate the role of the unstable Cdc7-regulatory protein Dbf4 in meiosis. We show that, when Dbf4 is depleted at the time of meiotic induction, cells enter the meiotic program but do not replicate their chromosomes. Surprisingly when Dbf4 is depleted after the initiation of DNA synthesis, S phase goes to completion, but most cells arrest before anaphase I. Deletion of the cohesin Rec8 suppresses this phenotype, suggesting a distinct role of DDK for meiotic chromosome segregation. As after Cdc5 depletion, a fraction of cells undergo a single equational division suggesting a failure to mono-orient sister kinetochores. Our results demonstrate that Dbf4 is essential for DNA replication during meiosis like in vegetative cells and provide evidence for an additional role in setting up the reductional division of meiosis I.
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Affiliation(s)
- Guillaume Valentin
- Institute of Molecular Genetics and Université Montpellier II, CNRS UMR5535-1919, Route de Mende, F-34293 Montpellier Cedex 5, France
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Abstract
Meiosis can be considered an elaboration of the cell division cycle in the sense that meiosis combines cell-cycle processes with programs specific to meiosis. Each phase of the cell division cycle is driven forward by cell-cycle kinases (Cdk) and coordinated with other phases of the cycle through checkpoint functions. Meiotic differentiation is also controlled by these two types of regulation; however, recent study in the budding yeast S. cerevisiae indicates that progression of meiosis is also controlled by a master regulator specific to meiosis, namely the Ime2p kinase. Below, I describe the overlapping roles of Ime2p and Cdk during meiosis in yeast and speculate on how these two kinases cooperate to drive the progression of meiosis.
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Affiliation(s)
- Saul M Honigberg
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri 64110-2499, USA.
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Affiliation(s)
- Randy Strich
- Program for Cell and Developmental Biology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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Abstract
Meiosis is the type of cell division that gives rise to eggs and sperm. Errors in the execution of this process can result in the generation of aneuploid gametes, which are associated with birth defects and infertility in humans. Here, we review recent findings on how cell-cycle controls ensure the coordination of meiotic events, with a particular focus on the segregation of chromosomes.
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Affiliation(s)
- Adèle L Marston
- Center for Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, E17-233, 40 Ames Street, Cambridge, Massachusetts 02139, USA
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Ofir Y, Sagee S, Guttmann-Raviv N, Pnueli L, Kassir Y. The role and regulation of the preRC component Cdc6 in the initiation of premeiotic DNA replication. Mol Biol Cell 2004; 15:2230-42. [PMID: 15004237 PMCID: PMC404018 DOI: 10.1091/mbc.e03-08-0617] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In all eukaryotes, the initiation of DNA replication is regulated by the ordered assembly of DNA/protein complexes on origins of DNA replication. In this report, we examine the role of Cdc6, a component of the prereplication complex, in the initiation of premeiotic DNA replication in budding yeast. We show that in the meiotic cycle, Cdc6 is required for DNA synthesis and sporulation. Moreover, similarly to the regulation in the mitotic cell cycle, Cdc6 is specifically degraded upon entry into the meiotic S phase. By contrast, chromatin-immunoprecipitation analysis reveals that the origin-bound Cdc6 is stable throughout the meiotic cycle. Preliminary evidence suggests that this protection reflects a change in chromatin structure that occurs in meiosis. Using the cdc28-degron allele, we show that depletion of Cdc28 leads to stabilization of Cdc6 in the mitotic cycle, but not in the meiotic cycle. We show physical association between Cdc6 and the meiosis-specific hCDK2 homolog Ime2. These results suggest that under meiotic conditions, Ime2, rather than Cdc28, regulates the stability of Cdc6. Chromatin-immunoprecipitation analysis reveals that similarly to the mitotic cell cycle, Mcm2 binds origins in G1 and meiotic S phases, and at the end of the second meiotic division, it is gradually removed from chromatin.
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Affiliation(s)
- Yaara Ofir
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000 Israel
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Abstract
To determine the extent to which eukaryotic replication origins are developmentally regulated in transcriptionally competent cells, we compared origin use in untreated growing amoebae and plasmodia of Physarum polycephalum. At loci that contain genes transcribed in both developmental stages, such as the ribosomal RNA genes and two unlinked actin genes, we show that there is a similar replicational organization, with the same origins used with comparable efficiencies, as shown by two-dimensional agarose-gel electrophoresis. By contrast, we found cell-type-specific replication patterns for the homologous, unlinked profilin A (proA) and profilin P (proP) genes. proA is replicated from a promoter-proximal origin in amoebae, in which it is highly expressed, and is replicated passively in the plasmodium, in which it is not expressed. Conversely, proP is replicated passively and is not expressed in amoebae, but coincides with an efficient origin when highly expressed in the plasmodium. Our results show a reprogramming of S phase that is linked to the reprogramming of transcription during Physarum cell differentiation. This is achieved by the use of two classes of promoter-associated replication origins: those that are constitutively active and those that are developmentally regulated. This suggests that replication origins, like genes, are under epigenetic control associated with cellular differentiation.
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Affiliation(s)
- Chrystelle Maric
- Institut André Lwoff, UPR-1983, Laboratoire Réplication de l'ADN et Ultrastructure du Noyau, 7 rue Guy Moquet, 94801 Villejuif, France
| | - Marianne Bénard
- Institut André Lwoff, UPR-1983, Laboratoire Réplication de l'ADN et Ultrastructure du Noyau, 7 rue Guy Moquet, 94801 Villejuif, France
| | - Gérard Pierron
- Institut André Lwoff, UPR-1983, Laboratoire Réplication de l'ADN et Ultrastructure du Noyau, 7 rue Guy Moquet, 94801 Villejuif, France
- Tel: +33 1 49 58 33 73; Fax +33 149 58 33 81;
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Abstract
The process of meiosis reduces a diploid cell to four haploid gametes and is accompanied by extensive recombination. Thus, chromosome dynamics in meiosis are significantly different than in mitotic cells. This review analyzes unique features of meiotic DNA replication and describes how it affects subsequent recombination and chromosome segregation.
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Affiliation(s)
- Susan L Forsburg
- Molecular and Cell Biology Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
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22
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Lindner K, Gregán J, Montgomery S, Kearsey SE. Essential role of MCM proteins in premeiotic DNA replication. Mol Biol Cell 2002; 13:435-44. [PMID: 11854402 PMCID: PMC65639 DOI: 10.1091/mbc.01-11-0537] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A critical event in eukaryotic DNA replication involves association of minichromosome maintenance (MCM2-7) proteins with origins, to form prereplicative complexes (pre-RCs) that are competent for initiation. The ability of mutants defective in MCM2-7 function to complete meiosis had suggested that pre-RC components could be irrelevant to premeiotic S phase. We show here that MCM2-7 proteins bind to chromatin in fission yeast cells preparing for meiosis and during premeiotic S phase in a manner suggesting they in fact are required for DNA replication in the meiotic cycle. This is confirmed by analysis of a degron mcm4 mutant, which cannot carry out premeiotic DNA replication. Later in meiosis, Mcm4 chromatin association is blocked between meiotic nuclear divisions, presumably accounting for the absence of a second round of DNA replication. Together, these results emphasize similarity between replication mechanisms in mitotic and meiotic cell cycles.
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Affiliation(s)
- Karola Lindner
- Department of Zoology, University of Oxford, Oxford, OX1 3PS United Kingdom
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Smith KN, Penkner A, Ohta K, Klein F, Nicolas A. B-type cyclins CLB5 and CLB6 control the initiation of recombination and synaptonemal complex formation in yeast meiosis. Curr Biol 2001; 11:88-97. [PMID: 11231124 DOI: 10.1016/s0960-9822(01)00026-4] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND The life cycle of most eukaryotic organisms includes a meiotic phase, in which diploid parental cells produce haploid gametes. During meiosis a single round of DNA replication is followed by two rounds of chromosome segregation. In the first, or reductional, division (meiosis I), which is unique to meiotic cells, homologous chromosomes segregate from one another, whereas in the second, or equational, division (Meiosis II) sister centromeres disjoin. Meiotic DNA replication precedes the initiation of recombination by programmed Spo11-dependent DNA double-strand breaks. Recent reports that meiosis-specific cohesion is established during meiotic S phase and that the length of S phase is modified by recombination factors (Spo11 and Rec8) raise the possibility that replication plays a fundamental role in the recombination process. RESULTS To address how replication influences the initiation of recombination, we have used mutations in the B-type cyclin genes CLB5 and CLB6, which specifically prevent premeiotic replication in the yeast Saccharomyces cerevisiae. We find that clb5 and clb5 clb6 but not clb6 mutants are defective in DSB induction and prior associated changes in chromatin accessibility, heteroallelic recombination, and SC formation. The severity of these phenotypes in each mutant reflects the extent of replication impairment. CONCLUSIONS This assemblage of phenotypes reveals roles for CLB5 and CLB6 not only in DNA replication but also in other key events of meiotic prophase. Links between the function of CLB5 and CLB6 in activating meiotic DNA replication and their effects on subsequent events are discussed.
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Affiliation(s)
- K N Smith
- Institut Curie, Section de Recherche, CNRS-UMR144 Cedex 05 75248, Paris, France
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24
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Forsburg SL, Hodson JA. Mitotic replication initiation proteins are not required for pre-meiotic S phase. Nat Genet 2000; 25:263-8. [PMID: 10888871 DOI: 10.1038/77015] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Initiation of mitotic DNA replication in eukaryotes requires conserved factors, including Cdc18/CDC6 and minichromosome maintenance (MCM) proteins. We show here that these proteins are not essential for meiotic DNA replication or subsequent meiotic divisions in fission yeast. In addition, vegetative replication checkpoint genes are not required for the arrest of meiotic divisions in response to pre-meiotic S-phase delays. Genes essential for other aspects of vegetative DNA replication, however, including polymerases and DNA ligase, are also required for pre-meiotic DNA synthesis. Our results indicate that the process of replication initiation and checkpoint control may be fundamentally different in mitotic and meiotic cells.
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Affiliation(s)
- S L Forsburg
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, USA.
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25
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Cha RS, Weiner BM, Keeney S, Dekker J, Kleckner N. Progression of meiotic DNA replication is modulated by interchromosomal interaction proteins, negatively by Spo11p and positively by Rec8p. Genes Dev 2000; 14:493-503. [PMID: 10691741 PMCID: PMC316381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Spo11p is a key mediator of interhomolog interactions during meiosis. Deletion of the SPO11 gene decreases the length of S phase by approximately 25%. Rec8p is a key coordinator of meiotic interhomolog and intersister interactions. Deletion of the REC8 gene increases S-phase length, by approximately 10% in wild-type and approximately 30% in a spo11Delta background. Thus, the progression of DNA replication is modulated by interchromosomal interaction proteins. The spo11-Y135F DSB (double strand break) catalysis-defective mutant is normal for S-phase modulation and DSB-independent homolog pairing but is defective for later events, formation of DSBs, and synaptonemal complexes. Thus, earlier and later functions of Spo11 are defined. We propose that meiotic S-phase progression is linked directly to development of specific chromosomal features required for meiotic interhomolog interactions and that this feedback process is built upon a more fundamental mechanism, common to all cell types, by which S-phase progression is coupled to development of nascent intersister connections and/or related aspects of chromosome morphogenesis. Roles for Rec8 and/or Spo11 in progression through other stages of meiosis are also revealed.
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Affiliation(s)
- R S Cha
- Department of Molecular Biology, Harvard University, Cambridge, Massachusetts 02138 USA
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26
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Abstract
In eukaryote, nuclear structure is a key component for the functions of eukaryotic cells. More and more evidences show that the nuclear structure plays important role in regulating DNA replication. The nuclear structure provides a physical barrier for the replication licensing, participates in the decision where DNA replication initiates, and organizes replication proteins as replication factory for DNA replication. Through these works, new concepts on the regulation of DNA replication have emerged, which will be discussed in this minireview.
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Affiliation(s)
- W J Rui
- Shanghai Institute of Biochemistry, Chinese Academy of Sciences, USA.
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27
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Grossmann KF, Brown JC, Moses RE. Cisplatin DNA cross-links do not inhibit S-phase and cause only a G2/M arrest in Saccharomyces cerevisiae. Mutat Res 1999; 434:29-39. [PMID: 10377946 DOI: 10.1016/s0921-8777(99)00011-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Cisplatin (CDDP) has been used as a DNA cross-linking agent to evaluate whether there is a specific cell cycle checkpoint response to such damage in Saccharomyces cerevisiae (S. cerevisiae). Fluorescent-activated cell sorting (FACS) analysis showed only a G2/M checkpoint, normal exit from G1 and progression through S-phase following alpha-factor arrest and CDDP treatment. Of the checkpoint mutants tested, rad9, rad17 and rad24, did not show increased sensitivity to CDDP compared to isogenic wild-type cells. However, other checkpoint mutants tested (mec1, mec3 and rad53) showed increased sensitivity to CDDP, as did controls with a defect in excision repair (rad1 and rad14) or a defect in recombination (rad51 and rad52). Thus, by survival and cell cycle kinetics, it appears that DNA cross-links do not inhibit entry into S-phase or slow DNA replication and that replication continues after cisplatin treatment in yeast.
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Affiliation(s)
- K F Grossmann
- Department of Molecular and Medical Genetics, Oregon Health Sciences University, Portland 97201, USA
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28
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Abstract
Saccharomyces cerevisiae can change its mating type as often as every generation by a highly choreographed, site-specific recombination event that replaces one MAT allele with different DNA sequences encoding the opposite allele. The study of this process has yielded important insights into the control of cell lineage, the silencing of gene expression, and the formation of heterochromatin, as well as the molecular events of double-strand break-induced recombination. In addition, MAT switching provides a remarkable example of a small locus control region--the Recombination Enhancer--that controls recombination along an entire chromosome arm.
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Affiliation(s)
- J E Haber
- Department of Biology, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
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29
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Abstract
Meiosis, a specialized cell division process, occurs in all sexually reproducing organisms. During this process a diploid cell undergoes a single round of DNA replication followed by two rounds of nuclear division to produce four haploid gametes. In yeast, the meiotic products are packaged into four spores that are enclosed in a sac known as an ascus. To enhance our understanding of the meiotic developmental pathway and spore formation, we followed differential expression of genes in meiotic versus vegetatively growing cells in the yeast Saccharomyces cerevisiae. Such comparative analyses have identified five different classes of genes that are expressed at different stages of the sporulation program. We identified several meiosis-specific genes including some already known to be induced during meiosis. Here we describe one of these previously uncharacterized genes, SSP1, which plays an essential role in meiosis and spore formation. SSP1 is induced midway through meiosis, and the homozygous mutant-diploid cells fail to sporulate. In ssp1 cells, meiosis is delayed, nuclei fragment after meiosis II, and viability declines rapidly. The ssp1 defect is not related to a microtubule-cytoskeletal-dependent event and is independent of two rounds of meiotic divisions. Our results suggest that Ssp1 is likely to function in a pathway that controls meiotic nuclear divisions and coordinates meiosis and spore formation. Functional analysis of other uncharacterized genes is underway.
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Affiliation(s)
- D K Nag
- Wadsworth Center, Department of Biomedical Sciences, School of Public Health, State University of New York, Albany 12201, USA
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30
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Ke N, Voytas DF. High frequency cDNA recombination of the saccharomyces retrotransposon Ty5: The LTR mediates formation of tandem elements. Genetics 1997; 147:545-56. [PMID: 9335592 PMCID: PMC1208177 DOI: 10.1093/genetics/147.2.545] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Retroelement cDNA can integrate into the genome using the element-encoded integrase or it can recombine with preexisting elements using the recombination system of the host. Recombination is a particularly important pathway for the yeast retrotransposon Ty5 and accounts for approximately 30% of the putative transposition events when a homologous substrate is carried on a plasmid and approximately 7% when the substrate is located at the chromosomal URA3 locus. Characterization of recombinants revealed that they are either simple replacements of the marker gene tandem elements. Using an assay system in which the donor element and recombination substrates are separated, we found that the long terminal repeats (LTRs) are critical for tandem element formation. LTR-containing substrates generate tandem elements at frequencies more than 10-fold higher than similarly sized internal Ty5 sequences. Internal sequences, however, facilitate tandem element formation when associated with an LTR, and there is a linear relationship between frequencies of tandem element formation and the length of LTR-containing substrates. We propose that recombination is initiated between the LTRs of the cDNA and substrate and that internal sequences promote tandem element formation by facilitating sequence alignment. Because of its location in subtelomeric regions, recombinational amplification of Ty5 may contribute to the organizations of chromosome ends.
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Affiliation(s)
- N Ke
- Department of Zoology and Genetics, Iowa State University, Ames 50011, USA
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31
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Holló G, Keresö J, Praznovszky T, Cserpán I, Fodor K, Katona R, Csonka E, Fátyol K, Szeles A, Szalay AA, Hadlaczky G. Evidence for a megareplicon covering megabases of centromeric chromosome segments. Chromosome Res 1996; 4:240-7. [PMID: 8793209 DOI: 10.1007/bf02254965] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have analysed the replication of the heterochromatic megachromosome that was formed de novo by a large-scale amplification process initiated in the centromeric region of mouse chromosome 7. The megachromosome is organized into amplicons approximately 30 Mb in size, and each amplicon consists of two large inverted repeats delimited by a primary replication initiation site. Our results suggest that these segments represent a higher order replication unit (megareplicon) of the centromeric region of mouse chromosomes. Analysis of the replication of the megareplicons indicates that the pericentric heterochromatin and the centromere of mouse chromosomes begin to replicate early, and that their replication continues through approximately three-quarters of the S-phase. We suggest that a replication-directed mechanism may account for the initiation of large-scale amplification in the centromeric regions of mouse chromosomes, and may also explain the formation of new, stable chromosome segments and chromosomes.
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Affiliation(s)
- G Holló
- Institute of Genetics, Hungarian Academy of Sciences, Szeged, Hungary
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32
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Affiliation(s)
- J F Diffley
- CRF Clare Hall Laboratories, South Mimms, U.K.
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33
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Sugawara N, Ivanov EL, Fishman-Lobell J, Ray BL, Wu X, Haber JE. DNA structure-dependent requirements for yeast RAD genes in gene conversion. Nature 1995; 373:84-6. [PMID: 7800045 DOI: 10.1038/373084a0] [Citation(s) in RCA: 141] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In Saccharomyces cerevisiae, HO endonuclease-induced mating-type (MAT) switching is a specialized mitotic recombination event in which MAT sequences are replaced by those copied from a distant, unexpressed donor (HML or HMR). The donors have a chromatin structure inaccessible for both transcription and HO cleavage. Here we use physical monitoring of DNA to show that MAT switching is completely blocked at an early step in recombination in strains deleted for the DNA repair genes RAD51, RAD52, RAD54, RAD55 or RAD57. We find, however, that only RAD52 is required when the donor sequence is simultaneously not silenced and located on a plasmid. RAD51, RAD54, RAD55 and RAD57 are still required when the same transcribed donor is on the chromosome. We conclude that recombination in vivo occurs between DNA molecules in chromatin, whose structure significantly influences the outcome. RAD51, RAD54, RAD55 and RAD57 are all required to facilitate strand invasion into otherwise inaccessible donor sequences.
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Affiliation(s)
- N Sugawara
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110
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34
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McCarroll RM, Esposito RE. SPO13 negatively regulates the progression of mitotic and meiotic nuclear division in Saccharomyces cerevisiae. Genetics 1994; 138:47-60. [PMID: 8001793 PMCID: PMC1206137 DOI: 10.1093/genetics/138.1.47] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The meiosis-specific yeast gene SPO13 has been previously shown to be required to obtain two successive divisions in meiosis. We report here that vegetative expression of this gene causes a CDC28-dependent cell-cycle arrest at mitosis. Overexpression of SPO13 during meiosis causes a transient block to completion of the meiosis I division and suppresses the inability of cdc28ts strains to execute meiosis II. The spo13 defect can be partially suppressed by conditions that slow progression of the first meiotic division. Based on the results presented below, we propose that SPO13 acts as a meiotic timing function by transiently blocking progression through the meiosis I division, thereby allowing (1) coordination of the first division with assembly of the reductional segregation apparatus, and (2) subsequent entry into a second round of segregation to separate replicated sister chromatids without an intervening S-phase.
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Affiliation(s)
- R M McCarroll
- Department of Radiation and Cellular Oncology, University of Chicago, Illinois 60637
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