scholarly journals Caenorhabditis elegans RMI2 functional homolog-2 (RMIF-2) and RMI1 (RMH-1) have both overlapping and distinct meiotic functions within the BTR complex

PLoS Genetics ◽  
2021 ◽  
Vol 17 (7) ◽  
pp. e1009663
Author(s):  
Maria Velkova ◽  
Nicola Silva ◽  
Maria Rosaria Dello Stritto ◽  
Alexander Schleiffer ◽  
Pierre Barraud ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Sister Chromatid ◽  
Meiotic Recombination ◽  
Sister Chromatid Exchange ◽  
Double Strand Breaks ◽  
Scaffolding Protein ◽  
Scaffolding Proteins ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Functional Homolog

Homologous recombination is a high-fidelity repair pathway for DNA double-strand breaks employed during both mitotic and meiotic cell divisions. Such repair can lead to genetic exchange, originating from crossover (CO) generation. In mitosis, COs are suppressed to prevent sister chromatid exchange. Here, the BTR complex, consisting of the Bloom helicase (HIM-6 in worms), topoisomerase 3 (TOP-3), and the RMI1 (RMH-1 and RMH-2) and RMI2 scaffolding proteins, is essential for dismantling joint DNA molecules to form non-crossovers (NCOs) via decatenation. In contrast, in meiosis COs are essential for accurate chromosome segregation and the BTR complex plays distinct roles in CO and NCO generation at different steps in meiotic recombination. RMI2 stabilizes the RMI1 scaffolding protein, and lack of RMI2 in mitosis leads to elevated sister chromatid exchange, as observed upon RMI1 knockdown. However, much less is known about the involvement of RMI2 in meiotic recombination. So far, RMI2 homologs have been found in vertebrates and plants, but not in lower organisms such as Drosophila, yeast, or worms. We report the identification of the Caenorhabditis elegans functional homolog of RMI2, which we named RMIF-2. The protein shows a dynamic localization pattern to recombination foci during meiotic prophase I and concentration into recombination foci is mutually dependent on other BTR complex proteins. Comparative analysis of the rmif-2 and rmh-1 phenotypes revealed numerous commonalities, including in regulating CO formation and directing COs toward chromosome arms. Surprisingly, the prevalence of heterologous recombination was several fold lower in the rmif-2 mutant, suggesting that RMIF-2 may be dispensable or less strictly required for some BTR complex-mediated activities during meiosis.

scholarly journals Double-strand breaks are not the main cause of spontaneous sister chromatid exchange in wild-type yeast cells

2017 ◽  
Author(s):  
Clémence Claussin ◽  
David Porubský ◽  
Diana C.J. Spierings ◽  
Nancy Halsema ◽  
Stefan Rentas ◽  
...  
Keyword(s):  
Sister Chromatid ◽  
Sister Chromatid Exchange ◽  
Genome Instability ◽  
Single Cells ◽  
Double Strand Breaks ◽  
Yeast Cells ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Template Strand ◽  
Sister Chromatids

SummaryHomologous recombination involving sister chromatids is the most accurate, and thus most frequently used, form of recombination-mediated DNA repair. Despite its importance, sister chromatid recombination is not easily studied because it does not result in a change in DNA sequence, making recombination between sister chromatids difficult to detect. We have previously developed a novel DNA template strand sequencing technique, called Strand-seq, that can be used to map sister chromatid exchange (SCE) events genome-wide in single cells. An increase in the rate of SCE is an indicator of elevated recombination activity and of genome instability, which is a hallmark of cancer. In this study, we have adapted Strand-seq to detect SCE in the yeast Saccharomyces cerevisiae. Contrary to what is commonly thought, we find that most spontaneous SCE events are not due to the repair of DNA double-strand breaks.

scholarly journals The cohesion protein ORD is required for homologue bias during meiotic recombination

2004 ◽  
Vol 164 (6) ◽  
pp. 819-829 ◽  
Author(s):  
Hayley A. Webber ◽  
Louisa Howard ◽  
Sharon E. Bickel
Keyword(s):  
Electron Microscopy ◽  
Homologous Recombination ◽  
Sister Chromatid ◽  
Meiotic Recombination ◽  
Sister Chromatid Exchange ◽  
Ring Chromosome ◽  
Double Strand Breaks ◽  
Wild Type ◽  
Strand Breaks ◽  
Chromatid Cohesion

During meiosis, sister chromatid cohesion is required for normal levels of homologous recombination, although how cohesion regulates exchange is not understood. Null mutations in orientation disruptor (ord) ablate arm and centromeric cohesion during Drosophila meiosis and severely reduce homologous crossovers in mutant oocytes. We show that ORD protein localizes along oocyte chromosomes during the stages in which recombination occurs. Although synaptonemal complex (SC) components initially associate with synapsed homologues in ord mutants, their localization is severely disrupted during pachytene progression, and normal tripartite SC is not visible by electron microscopy. In ord germaria, meiotic double strand breaks appear and disappear with frequency and timing indistinguishable from wild type. However, Ring chromosome recovery is dramatically reduced in ord oocytes compared with wild type, which is consistent with the model that defects in meiotic cohesion remove the constraints that normally limit recombination between sisters. We conclude that ORD activity suppresses sister chromatid exchange and stimulates inter-homologue crossovers, thereby promoting homologue bias during meiotic recombination in Drosophila.

scholarly journals Targeted Gene Knockout Reveals a Role in Meiotic Recombination for ZHP-3, a Zip3-Related Protein in Caenorhabditis elegans

2004 ◽  
Vol 24 (18) ◽  
pp. 7998-8006 ◽  
Author(s):  
Verena Jantsch ◽  
Pawel Pasierbek ◽  
Michael M. Mueller ◽  
Dieter Schweizer ◽  
Michael Jantsch ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Meiotic Recombination ◽  
Fluorescent Protein ◽  
Gene Knockout ◽  
Chiasma Formation ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
C Elegans ◽  
Reciprocal Recombination

ABSTRACT The meiotically expressed Zip3 protein is found conserved from Saccharomyces cerevisiae to humans. In baker's yeast, Zip3p has been implicated in synaptonemal complex (SC) formation, while little is known about the protein's function in multicellular organisms. We report here the successful targeted gene disruption of zhp-3 (K02B12.8), the ZIP3 homolog in the nematode Caenorhabditis elegans. Homozygous zhp-3 knockout worms show normal homologue pairing and SC formation. Also, the timing of appearance and the nuclear localization of the recombination protein Rad-51 seem normal in these animals, suggesting proper initiation of meiotic recombination by DNA double-strand breaks. However, the occurrence of univalents during diplotene indicates that C. elegans ZHP-3 protein is essential for reciprocal recombination between homologous chromosomes and thus chiasma formation. In the absence of ZHP-3, reciprocal recombination is abolished and double-strand breaks seem to be repaired via alternative pathways, leading to achiasmatic chromosomes and the occurrence of univalents during meiosis I. Green fluorescent protein-tagged C. elegans ZHP-3 forms lines between synapsed chromosomes and requires the SC for its proper localization.

scholarly journals Epigenetic activation of meiotic recombination in Arabidopsis centromeres via loss of H3K9me2 and non-CG DNA methylation

2017 ◽  
Author(s):  
Charles J. Underwood ◽  
Kyuha Choi ◽  
Christophe Lambing ◽  
Xiaohui Zhao ◽  
Heïdi Serra ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Meiotic Recombination ◽  
Double Strand Breaks ◽  
Pericentromeric Heterochromatin ◽  
Repair Pathway ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Histone 3 ◽  
Differential Control

AbstractEukaryotic centromeres contain the kinetochore, which connects chromosomes to the spindle allowing segregation. During meiosis centromeres are suppressed for crossovers, as recombination in these regions can cause chromosome mis-segregation. Plant centromeres are surrounded by repetitive, transposon-dense heterochromatin that is epigenetically silenced by histone 3 lysine 9 dimethylation (H3K9me2), and DNA methylation in CG and non-CG sequence contexts. Here we show that disruption of Arabidopsis H3K9me2 and non-CG DNA methylation pathways increases meiotic DNA double strand breaks (DSBs) within centromeres, whereas crossovers increase within pericentromeric heterochromatin. Increased pericentromeric crossovers in H3K9me2/non-CG mutants occurs in both inbred and hybrid backgrounds, and involves the interfering crossover repair pathway. Epigenetic activation of recombination may also account for the curious tendency of maize transposon Ds to disrupt CHROMOMETHYLASE3 when launched from proximal loci. Thus H3K9me2 and non-CG DNA methylation exert differential control of meiotic DSB and crossover formation in centromeric and pericentromeric heterochromatin.

Double-strand-break-induced homologous recombination in mammalian cells

2001 ◽  
Vol 29 (2) ◽  
pp. 196-201 ◽  
Author(s):  
R. D. Johnson ◽  
M. Jasin
Keyword(s):  
Homologous Recombination ◽  
Sister Chromatid ◽  
Mammalian Cells ◽  
Indirect Evidence ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Crossing Over ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Strand Breaks

In mammalian cells, the repair of DNA double-strand breaks (DSBs) occurs by both homologous and non-homologous mechanisms. Indirect evidence, including that from gene targeting and random integration experiments, had suggested that non-homologous mechanisms were significantly more frequent than homologous ones. However, more recent experiments indicate that homologous recombination is also a prominent DSB repair pathway. These experiments show that mammalian cells use homologous sequences located at multiple positions throughout the genome to repair a DSB. However, template preference appears to be biased, with the sister chromatid being preferred by 2–3 orders of magnitude over a homologous or heterologous chromosome. The outcome of homologous recombination in mammalian cells is predominantly gene conversion that is not associated with crossing-over. The preference for the sister chromatid and the bias against crossing-over seen in mitotic mammalian cells may have developed in order to reduce the potential for genome alterations that could occur when other homologous repair templates are utilized. In attempts to understand further the mechanism of homologous recombination, the proteins that promote this process are beginning to be identified. To date, four mammalian proteins have been demonstrated conclusively to be involved in DSB repair by homologous recombination: Rad54, XRCC2, XRCC3 and BRCAI. This paper summarizes results from a number of recent studies.

scholarly journals A global view of meiotic double-strand break end resection

Science ◽  
2017 ◽  
Vol 355 (6320) ◽  
pp. 40-45 ◽  
Author(s):  
Eleni P. Mimitou ◽  
Shintaro Yamada ◽  
Scott Keeney
Keyword(s):  
Meiotic Recombination ◽  
Strand Break ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Naked Dna ◽  
Global View ◽  
Genome Wide ◽  
End Resection

DNA double-strand breaks that initiate meiotic recombination are exonucleolytically processed. This 5′→3′ resection is a central, conserved feature of recombination but remains poorly understood. To address this lack, we mapped resection endpoints genome-wide at high resolution inSaccharomyces cerevisiae. Full-length resection requires Exo1 exonuclease and the DSB-responsive kinase Tel1, but not Sgs1 helicase. Tel1 also promotes efficient and timely resection initiation. Resection endpoints display pronounced heterogeneity between genomic loci that reflects a tendency for nucleosomes to block Exo1, yet Exo1 also appears to digest chromatin with high processivity and at rates similar to naked DNA in vitro. This paradox points to nucleosome destabilization or eviction as a defining feature of the meiotic resection landscape.

scholarly journals Multiple Genetic Pathways Involving the Caenorhabditis elegans Bloom's Syndrome Genes him-6, rad-51, and top-3 Are Needed To Maintain Genome Stability in the Germ Line

2004 ◽  
Vol 24 (11) ◽  
pp. 5016-5027 ◽  
Author(s):  
Chantal Wicky ◽  
Arno Alpi ◽  
Myriam Passannante ◽  
Ann Rose ◽  
Anton Gartner ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Germ Cells ◽  
Meiotic Recombination ◽  
Germ Line ◽  
Genetic Interaction ◽  
Double Strand Breaks ◽  
Mitotic Catastrophe ◽  
Bloom's Syndrome ◽  
Strand Breaks ◽  
Bloom’S Syndrome

ABSTRACT Bloom's syndrome (BS) is an autosomal-recessive human disorder caused by mutations in the BS RecQ helicase and is associated with loss of genomic integrity and an increased incidence of cancer. We analyzed the mitotic and the meiotic roles of Caenorhabditis elegans him-6, which we show to encode the ortholog of the human BS gene. Mutations in him-6 result in an enhanced irradiation sensitivity, a partially defective S-phase checkpoint, and in reduced levels of DNA-damage induced apoptosis. Furthermore, him-6 mutants exhibit a decreased frequency of meiotic recombination that is probably due to a defect in the progression of crossover recombination. In mitotically proliferating germ cells, our genetic interaction studies, as well as the assessment of the number of double-strand breaks via RAD-51 foci, reveal a complex regulatory network that is different from the situation in yeast. Although the number of double-strand breaks in him-6 and top-3 single mutants is elevated, the combined depletion of him-6 and top-3 leads to mitotic catastrophe concomitant with a massive increase in the level of double-strand breaks, a phenotype that is completely suppressed by rad-51. him-6 and top-3 are thus needed to maintain low levels of double-strand breaks in normally proliferating germ cells, and both act in partial redundant pathways downstream of rad-51 to prevent mitotic catastrophy. Finally, we show that topoisomerase IIIα acts independently during a late stage of meiotic recombination.

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