Exo1-protected DNA nicks direct crossover formation in meiosis

In most sexually reproducing organisms crossing over between chromosome homologs during meiosis is critical for the viability of haploid gametes. Most crossovers that form in meiosis in budding yeast result from the biased resolution of double Holliday Junction (dHJ) intermediates. This dHJ resolution step involves the actions Rad2/XPG family nuclease Exo1 and the Mlh1- Mlh3 mismatch repair endonuclease. At present little is known about how these factors act in meiosis at the molecular level. Here we show that Exo1 promotes meiotic crossing over by protecting DNA nicks from ligation. We found that structural elements in Exo1 required for interactions with DNA, such as bending of DNA during nick/flap recognition, are critical for its role in crossing over. Consistent with these observations, meiotic expression of the Rad2/XPG family member Rad27 partially rescued the crossover defect in exo1 null mutants, and meiotic overexpression of Cdc9 ligase specifically reduced the crossover levels of exo1 DNA binding mutants to levels approaching the exo1 null. In addition, our work identified a role for Exo1 in crossover interference that appears independent of its resection activity. Together, these studies provide experimental evidence for Exo1 protected nicks being critical for the formation of meiotic crossovers and their distribution.

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The Mus81/Mms4 Endonuclease Acts Independently of Double-Holliday Junction Resolution to Promote a Distinct Subset of Crossovers During Meiosis in Budding Yeast

Genetics ◽

10.1093/genetics/164.1.81 ◽

2003 ◽

Vol 164 (1) ◽

pp. 81-94 ◽

Cited By ~ 21

Author(s):

Teresa de los Santos ◽

Neil Hunter ◽

Cindy Lee ◽

Brittany Larkin ◽

Josef Loidl ◽

...

Keyword(s):

Budding Yeast ◽

Indirect Evidence ◽

Class Ii ◽

Suppressive Effect ◽

Class I ◽

Holliday Junction ◽

Crossing Over ◽

Crossover Interference ◽

Distinct Subset ◽

Double Holliday Junction

Abstract Current models for meiotic recombination require that crossovers derive from the resolution of a double-Holliday junction (dHJ) intermediate. In prokaryotes, enzymes responsible for HJ resolution are well characterized but the identification of a eukaryotic nuclear HJ resolvase has been elusive. Indirect evidence suggests that MUS81 from humans and fission yeast encodes a HJ resolvase. We provide three lines of evidence that Mus81/Mms4 is not the major meiotic HJ resolvase in S. cerevisiae: (1) MUS81/MMS4 is required to form only a distinct subset of crossovers; (2) rather than accumulating, dHJ intermediates are reduced in an mms4 mutant; and (3) expression of a bacterial HJ resolvase has no suppressive effect on mus81 meiotic phenotypes. Our analysis also reveals the existence of two distinct classes of crossovers in budding yeast. Class I is dependent upon MSH4/MSH5 and exhibits crossover interference, while class II is dependent upon MUS81/MMS4 and exhibits no interference. mms4 specifically reduces crossing over on small chromosomes, which are known to undergo less interference. The correlation between recombination rate and degree of interference to chromosome size may therefore be achieved by modulating the balance between class I/class II crossovers.

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Control of meiotic recombination in Arabidopsis: role of the MutL and MutS homologues

Biochemical Society Transactions ◽

10.1042/bst0340542 ◽

2006 ◽

Vol 34 (4) ◽

pp. 542-544 ◽

Cited By ~ 23

Author(s):

F.C.H. Franklin ◽

J.D. Higgins ◽

E. Sanchez-Moran ◽

S.J. Armstrong ◽

K.E. Osman ◽

...

Keyword(s):

Mismatch Repair ◽

Meiotic Recombination ◽

Holliday Junction ◽

Crossing Over ◽

Wild Type ◽

Pathway Model ◽

Junction Formation ◽

Double Holliday Junction ◽

Dependent Pathway

Immunocytochemistry reveals that the Arabidopsis mismatch repair proteins AtMSH4, AtMLH3 and AtMLH1 are expressed during prophase I of meiosis. Expression of AtMSH4 precedes AtMLH3 and AtMLH1 which co-localize as foci during pachytene. Co-localization between AtMSH4 and AtMLH3 occurs, but appears transient. AtMLH3 foci are not detected in an Atmsh4 mutant. However, localization of AtMSH4 is unaffected in Atmlh3, suggesting that recombination may proceed to dHj (double Holliday junction) formation. Mean chiasma frequency in Atmsh4 is reduced to 1.55 compared with 9.86 in wild-type. In contrast with wild-type, the distribution of residual crossovers in Atmsh4 closely fits a Poisson distribution. This is consistent with a two-pathway model for meiotic crossing-over whereby most crossovers occur via an AtMSH4-dependent pathway that is subject to interference, with the remaining crossovers arising via an interference-independent pathway. Loss of AtMLH3 results in an approx. 60% reduction in crossovers. Results suggest that dHj resolution can occur, but in contrast with wild-type where most or all dHjs are directed to form crossovers, the outcome is biased in favour of a non-crossover outcome. The results are compatible with a model whereby the MutL complex maintains or imposes a dHj conformation that ensures crossover formation.

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The Budding Yeast Msh4 Protein Functions in Chromosome Synapsis and the Regulation of Crossover Distribution

Genetics ◽

10.1093/genetics/158.3.1013 ◽

2001 ◽

Vol 158 (3) ◽

pp. 1013-1025 ◽

Cited By ~ 7

Author(s):

Janet E Novak ◽

Petra B Ross-Macdonald ◽

G Shirleen Roeder

Keyword(s):

Mismatch Repair ◽

Budding Yeast ◽

Null Mutation ◽

Crossing Over ◽

Wild Type ◽

Crossover Interference ◽

Meiotic Chromosomes ◽

Chromosome Synapsis ◽

Protein Functions ◽

Or Gene

AbstractThe budding yeast MSH4 gene encodes a MutS homolog produced specifically in meiotic cells. Msh4 is not required for meiotic mismatch repair or gene conversion, but it is required for wild-type levels of crossing over. Here, we show that a msh4 null mutation substantially decreases crossover interference. With respect to the defect in interference and the level of crossing over, msh4 is similar to the zip1 mutant, which lacks a structural component of the synaptonemal complex (SC). Furthermore, epistasis tests indicate that msh4 and zip1 affect the same subset of meiotic crossovers. In the msh4 mutant, SC formation is delayed compared to wild type, and full synapsis is achieved in only about half of all nuclei. The simultaneous defects in synapsis and interference observed in msh4 (and also zip1 and ndj1/tam1) suggest a role for the SC in mediating interference. The Msh4 protein localizes to discrete foci on meiotic chromosomes and colocalizes with Zip2, a protein involved in the initiation of chromosome synapsis. Both Zip2 and Zip1 are required for the normal localization of Msh4 to chromosomes, raising the possibility that the zip1 and zip2 defects in crossing over are indirect, resulting from the failure to localize Msh4 properly.

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The Conversion Gradient at HIS4 of Saccharomyces cerevisiae. II. A Role for Mismatch Repair Directed by Biased Resolution of the Recombinational Intermediate

Genetics ◽

10.1093/genetics/153.2.573 ◽

1999 ◽

Vol 153 (2) ◽

pp. 573-583 ◽

Cited By ~ 10

Author(s):

Henriette M Foss ◽

Kenneth J Hillers ◽

Franklin W Stahl

Keyword(s):

Saccharomyces Cerevisiae ◽

Dna Synthesis ◽

Mismatch Repair ◽

Strand Break ◽

Double Strand Break ◽

Double Strand Break Repair ◽

Holliday Junction ◽

Crossing Over ◽

Gradient Type ◽

Salient Features

AbstractSalient features of recombination at ARG4 of Saccharomyces provoke a variation of the double-strand-break repair (DSBR) model that has the following features: (1) Holliday junction cutting is biased in favor of strands upon which DNA synthesis occurred during formation of the joint molecule (this bias ensures that cutting both junctions of the joint-molecule intermediate arising during DSBR usually leads to crossing over); (2) cutting only one junction gives noncrossovers; and (3) repair of mismatches that are semirefractory to mismatch repair and/or far from the DSB site is directed primarily by junction resolution. The bias in junction resolution favors restoration of 4:4 segregation when such mismatches and the directing junction are on the same side of the DSB site. Studies at HIS4 confirmed the predicted influence of the bias in junction resolution on the conversion gradient, type of mismatch repair, and frequency of aberrant 5:3 segregation, as well as the predicted relationship between mismatch repair and crossing over.

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Regulation of Msh4-Msh5 association with meiotic chromosomes in budding yeast

Genetics ◽

10.1093/genetics/iyab102 ◽

2021 ◽

Author(s):

Krishnaprasad G Nandanan ◽

Sagar Salim ◽

Ajith V Pankajam ◽

Miki Shinohara ◽

Gen Lin ◽

...

Keyword(s):

Binding Sites ◽

Holliday Junction ◽

Crossing Over ◽

Wild Type ◽

Yeast Saccharomyces Cerevisiae ◽

Meiotic Chromosomes ◽

Genome Wide ◽

Double Holliday Junction

Abstract In the baker’s yeast Saccharomyces cerevisiae, most of the meiotic crossovers are generated through a pathway involving the highly conserved mismatch repair related Msh4-Msh5 complex. To understand the role of Msh4-Msh5 in meiotic crossing over, we determined its genome wide in vivo binding sites in meiotic cells. We show that Msh5 specifically associates with DSB hotspots, chromosome axes, and centromeres on chromosomes. A basal level of Msh5 association with these chromosomal features is observed even in the absence of DSB formation (spo11Δ mutant) at the early stages of meiosis. But efficient binding to DSB hotspots and chromosome axes requires DSB formation and resection and is enhanced by double Holliday junction structures. Msh5 binding is also correlated to DSB frequency and enhanced on small chromosomes with higher DSB and crossover density. The axis protein Red1 is required for Msh5 association with the chromosome axes and DSB hotspots but not centromeres. Although binding sites of Msh5 and other pro-crossover factors like Zip3 show extensive overlap, Msh5 associates with centromeres independent of Zip3. These results on Msh5 localization in wild type and meiotic mutants have implications for how Msh4-Msh5 works with other pro-crossover factors to ensure crossover formation.

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Mismatch repair impedes meiotic crossover interference

10.1101/480418 ◽

2018 ◽

Cited By ~ 4

Author(s):

Tim J. Cooper ◽

Margaret R. Crawford ◽

Laura J. Hunt ◽

Marie-Claude Marsolier-Kergoat ◽

Bertrand Llorente ◽

...

Keyword(s):

Mismatch Repair ◽

Dna Sequence ◽

Meiotic Recombination ◽

Molecular Level ◽

Computational Modelling ◽

Sequence Divergence ◽

Global Distribution ◽

Crossover Interference ◽

Genome Wide ◽

Meiotic Crossover

SummarySequence divergence, mediated by the anti-recombinogenic activity of mismatch repair (MMR), forms a potent barrier to meiotic recombination and in turn the formation of viable gametes1–5. However, exactly how MMR jeopardizes meiotic success is unclear. Here we utilize a combination ofS. cerevisiaegenetics, genome-wide mapping of recombination and computational modelling to demonstrate that MMR unexpectedly influences the global distribution of recombination through preferential suppression of interfering crossovers (COs) at regions of greater sequence divergence. As a result, inactivation of MMR not only increases the rate of recombination, as previously observed, but also, paradoxically, the strength of CO interference. Our observations reveal a new mechanism by which MMR spatially sculpts the meiotic landscape—linking CO control to the mechanisms that can reproductively isolate a population, and highlighting how genomes may become meiotically incompatible at the molecular level, dependent upon interactions of the primary DNA sequence.

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Faculty Opinions recommendation of Template disruptions and failure of double Holliday junction dissolution during double-strand break repair in Drosophila BLM mutants.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1052711.504623 ◽

2006 ◽

Author(s):

Lorraine Symington

Keyword(s):

Strand Break ◽

Double Strand Break ◽

Double Strand Break Repair ◽

Holliday Junction ◽

Break Repair ◽

Double Holliday Junction

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Crossover Interference in Arabidopsis

Genetics ◽

10.1093/genetics/160.4.1631 ◽

2002 ◽

Vol 160 (4) ◽

pp. 1631-1639 ◽

Cited By ~ 6

Author(s):

G P Copenhaver ◽

E A Housworth ◽

F W Stahl

Keyword(s):

Arabidopsis Thaliana ◽

Degrees Of Freedom ◽

Double Strand Breaks ◽

Crossing Over ◽

Chi Square ◽

Strand Breaks ◽

Crossover Interference

AbstractThe crossover distribution in meiotic tetrads of Arabidopsis thaliana differs from those previously described for Drosophila and Neurospora. Whereas a chi-square distribution with an even number of degrees of freedom provides a good fit for the latter organisms, the fit for Arabidopsis was substantially improved by assuming an additional set of crossovers sprinkled, at random, among those distributed as per chi square. This result is compatible with the view that Arabidopsis has two pathways for meiotic crossing over, only one of which is subject to interference. The results further suggest that Arabidopsis meiosis has >10 times as many double-strand breaks as crossovers.

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