scholarly journals The conserved LEM-3/Ankle1 nuclease is involved in the combinatorial regulation of meiotic recombination repair and chromosome segregation in Caenorhabditis elegans

2017 ◽  
Author(s):  
Ye Hong ◽  
Maria Velkova ◽  
Nicola Silva ◽  
Marlène Jagut ◽  
Viktor Scheidt ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Holliday Junctions ◽  
Combinatorial Regulation ◽  
Strand Breaks ◽  
C Elegans ◽  
Repair Enzymes ◽  
Recombination Repair ◽  
Chromatin Bridges

AbstractHomologous recombination is essential for crossover (CO) formation and accurate chromosome segregation during meiosis. It is of considerable importance to work out how recombination intermediates are processed leading to CO and non-crossover (NCO) outcome. Genetic analysis in budding yeast and Caenorhabditis elegans indicates that the processing of meiotic recombination intermediates involves a combination of nucleases and DNA repair enzymes. We previously reported that in C. elegans meiotic Holiday junction resolution is mediated by two redundant pathways, conferred by the SLX-1 and MUS-81 nucleases, and by the HIM-6 Blooms helicase in conjunction with the XPF-1 endonucleases, respectively. Both pathways require the scaffold protein SLX-4. However, in the absence of all these enzymes residual processing of meiotic recombination intermediates still occurs and CO formation is reduced but not abolished. Here we show that the LEM-3 nuclease, mutation of which by itself does not have an overt meiotic phenotype, genetically interacts with slx-1 and mus-81 mutants, the respective double mutants leading to 100% embryonic lethality. LEM-3 and MUS-81 act redundantly, their combined loss leading to a reduced number of early meiotic recombination intermediates, to a delayed disassembly of foci associated with CO designated sites, and to the formation of univalents linked by SPO-11 dependent chromatin bridges (dissociated bivalents). However, LEM-3 foci do not co-localize with ZHP-3 a marker that congresses into CO designated sites. In addition, neither CO frequency nor distribution is altered in lem-3 single mutants or in combination with mus-81 or slx-4 mutations, indicating that LEM-3 drives NCO outcome. Finally, we found persistent chromatin bridges during meiotic divisions in lem-3; slx-4 double mutants. Supported by the localization of LEM-3 between dividing meiotic nuclei, this data suggests that LEM-3 is able to process erroneous recombination intermediates that persist into the second meiotic divisions.Author SummaryMeiotic recombination is required for genetic diversity and for the proper chromosome segregation. Recombination intermediates, such as Holliday junctions (HJs), are generated and eventually resolved to produce crossover (CO) and non-crossover (NCO). While an excess of meiotic double-strand breaks is generated, most breaks are repaired without leading to a CO outcome and usually only one break for each chromosome pair matures into a CO-designated site in Caenorhabditis elegans. Resolution of meiotic recombination intermediates and CO formation have been reported to be highly regulated by several structure-specific endonucleases and the Bloom helicase. However, little is known about enzymes involved in the NCO recombination intermediate resolution. In this study, we found that a conserved nuclease LEM-3/Ankle1 acts in parallel to the SLX-1/MUS-81 pathway to process meiotic recombination intermediates. Mutation of lem-3 has no effect on CO frequency and distribution, indicating LEM-3 functions as a nuclease promoting NCO outcome. Interestingly, a prominent localization of LEM-3 is found between dividing meiotic nuclei. We provide evidence that LEM-3 is also involved in processing remaining, erroneous recombination intermediates during meiotic divisions.

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 In vivo analysis of FANCD2 recruitment at meiotic DNA breaks in Caenorhabditis elegans

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Marcello Germoglio ◽  
Anna Valenti ◽  
Ines Gallo ◽  
Chiara Forenza ◽  
Pamela Santonicola ◽  
...  
Keyword(s):  
Dna Repair ◽  
Caenorhabditis Elegans ◽  
Genome Stability ◽  
Genetic Interaction ◽  
Model Systems ◽  
Dna Breaks ◽  
Strand Breaks ◽  
C Elegans ◽  
In Vivo Analysis

AbstractFanconi Anemia is a rare genetic disease associated with DNA repair defects, congenital abnormalities and infertility. Most of FA pathway is evolutionary conserved, allowing dissection and mechanistic studies in simpler model systems such as Caenorhabditis elegans. In the present study, we employed C. elegans to better understand the role of FA group D2 (FANCD2) protein in vivo, a key player in promoting genome stability. We report that localization of FCD-2/FANCD2 is dynamic during meiotic prophase I and requires its heterodimeric partner FNCI-1/FANCI. Strikingly, we found that FCD-2 recruitment depends on SPO-11-induced double-strand breaks (DSBs) but not RAD-51-mediated strand invasion. Furthermore, exposure to DNA damage-inducing agents boosts FCD-2 recruitment on the chromatin. Finally, analysis of genetic interaction between FCD-2 and BRC-1 (the C. elegans orthologue of mammalian BRCA1) supports a role for these proteins in different DSB repair pathways. Collectively, we showed a direct involvement of FCD-2 at DSBs and speculate on its function in driving meiotic DNA repair.

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.

scholarly journals Caenorhabditis elegans DSB-3 reveals conservation and divergence among protein complexes promoting meiotic double-strand breaks

2021 ◽  
Vol 118 (33) ◽  
pp. e2109306118
Author(s):  
Albert W. Hinman ◽  
Hsin-Yi Yeh ◽  
Baptiste Roelens ◽  
Kei Yamaya ◽  
Alexander Woglar ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Meiotic Recombination ◽  
Protein Complexes ◽  
Meiotic Chromosome ◽  
Structured Illumination ◽  
Dna Breaks ◽  
Structured Illumination Microscopy ◽  
Strand Breaks ◽  
Double Strand Dna Breaks ◽  
Essential Components

Meiotic recombination plays dual roles in the evolution and stable inheritance of genomes: Recombination promotes genetic diversity by reassorting variants, and it establishes temporary connections between pairs of homologous chromosomes that ensure their future segregation. Meiotic recombination is initiated by generation of double-strand DNA breaks (DSBs) by the conserved topoisomerase-like protein Spo11. Despite strong conservation of Spo11 across eukaryotic kingdoms, auxiliary complexes that interact with Spo11 complexes to promote DSB formation are poorly conserved. Here, we identify DSB-3 as a DSB-promoting protein in the nematode Caenorhabditis elegans. Mutants lacking DSB-3 are proficient for homolog pairing and synapsis but fail to form crossovers. Lack of crossovers in dsb-3 mutants reflects a requirement for DSB-3 in meiotic DSB formation. DSB-3 concentrates in meiotic nuclei with timing similar to DSB-1 and DSB-2 (predicted homologs of yeast/mammalian Rec114/REC114), and DSB-1, DSB-2, and DSB-3 are interdependent for this localization. Bioinformatics analysis and interactions among the DSB proteins support the identity of DSB-3 as a homolog of MEI4 in conserved DSB-promoting complexes. This identification is reinforced by colocalization of pairwise combinations of DSB-1, DSB-2, and DSB-3 foci in structured illumination microscopy images of spread nuclei. However, unlike yeast Rec114, DSB-1 can interact directly with SPO-11, and in contrast to mouse REC114 and MEI4, DSB-1, DSB-2, and DSB-3 are not concentrated predominantly at meiotic chromosome axes. We speculate that variations in the meiotic program that have coevolved with distinct reproductive strategies in diverse organisms may contribute to and/or enable diversification of essential components of the meiotic machinery.

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 CSC-1

2003 ◽  
Vol 161 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Alper Romano ◽  
Annika Guse ◽  
Ivica Krascenicova ◽  
Heinke Schnabel ◽  
Ralf Schnabel ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Genetic Analysis ◽  
Chromosome Segregation ◽  
Kinase Activity ◽  
Aurora B ◽  
Aurora B Kinase ◽  
C Elegans ◽  
The Individual

The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

scholarly journals RMD-1, a novel microtubule-associated protein, functions in chromosome segregation in Caenorhabditis elegans

2007 ◽  
Vol 179 (6) ◽  
pp. 1149-1162 ◽  
Author(s):  
Kumiko Oishi ◽  
Hideyuki Okano ◽  
Hitoshi Sawa
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Growth Defect ◽  
Aurora B ◽  
C Elegans ◽  
Spindle Poles ◽  
Protein Functions ◽  
Microtubule Growth ◽  
Mild Defect

For proper chromosome segregation, the sister kinetochores must attach to microtubules extending from the opposite spindle poles. Any errors in microtubule attachment can induce aneuploidy. In this study, we identify a novel conserved Caenorhabditis elegans microtubule-associated protein, regulator of microtubule dynamics 1 (RMD-1), that localizes to spindle microtubules and spindle poles. Depletion of RMD-1 induces severe defects in chromosome segregation, probably through merotelic attachments between microtubules and chromosomes. Although rmd-1 embryos also have a mild defect in microtubule growth, we find that mutants of the microtubule growth regulator XMAP215/ZYG-9 show much weaker segregation defects. This suggests that the microtubule growth defect in rmd-1 embryos does not cause abnormal chromosome segregation. We also see that RMD-1 interacts with aurora B in vitro. Our results suggest that RMD-1 functions in chromosome segregation in C. elegans embryos, possibly through the aurora B–mediated pathway. Human homologues of RMD-1 could also bind microtubules, which would suggest a function for these proteins in chromosome segregation during mitosis in other organisms as well.

scholarly journals Activation of meiotic recombination by nuclear import of the DNA break hotspot-determining complex in fission yeast

2021 ◽  
Vol 134 (4) ◽  
pp. jcs253518 ◽  
Author(s):  
Mélody Wintrebert ◽  
Mai-Chi Nguyen ◽  
Gerald R. Smith
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
High Specificity ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Nuclear Entry ◽  
Strand Breaks ◽  
Protein Complex Formation ◽  
Complex Process ◽  
Localization Signal

ABSTRACTMeiotic recombination forms crossovers important for proper chromosome segregation and offspring viability. This complex process involves many proteins acting at each of the multiple steps of recombination. Recombination initiates by formation of DNA double-strand breaks (DSBs), which in the several species examined occur with high frequency at special sites (DSB hotspots). In Schizosaccharomyces pombe, DSB hotspots are bound with high specificity and strongly activated by linear element (LinE) proteins Rec25, Rec27 and Mug20, which form colocalized nuclear foci with Rec10, essential for all DSB formation and recombination. Here, we test the hypothesis that the nuclear localization signal (NLS) of Rec10 is crucial for coordinated nuclear entry after forming a complex with other LinE proteins. In NLS mutants, all LinE proteins were abundant in the cytoplasm, not the nucleus; DSB formation and recombination were much reduced but not eliminated. Nuclear entry of limited amounts of Rec10, apparently small enough for passive nuclear entry, can account for residual recombination. LinE proteins are related to synaptonemal complex proteins of other species, suggesting that they also share an NLS, not yet identified, and undergo protein complex formation before nuclear entry.This article has an associated First Person interview with Mélody Wintrebert, joint first author of the paper.

Making crossovers during meiosis

2005 ◽  
Vol 33 (6) ◽  
pp. 1451-1455 ◽  
Author(s):  
M.C. Whitby
Keyword(s):  
Genetic Variation ◽  
Homologous Recombination ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Meiotic Division ◽  
Holliday Junctions ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Dna Junctions

Homologous recombination (HR) is required to promote both correct chromosome segregation and genetic variation during meiosis. For this to be successful recombination intermediates must be resolved to generate reciprocal exchanges or ‘crossovers’ between the homologous chromosomes (homologues) during the first meiotic division. Crossover recombination promotes faithful chromosome segregation by establishing connections (chiasmata) between the homologues, which help guide their proper bipolar alignment on the meiotic spindle. Recent studies of meiotic recombination in both the budding and fission yeasts have established that there are at least two pathways for generating crossovers. One pathway involves the resolution of fully ligated four-way DNA junctions [HJs (Holliday junctions)] by an as yet unidentified endonuclease. The second pathway appears to involve the cleavage of the precursors of ligated HJs, namely displacement (D) loops and unligated/nicked HJs, by the Mus81-Eme1/Mms4 endonuclease.

Sign in / Sign up

Export Citation Format

Share Document