Exo1 protects DNA nicks from ligation to promote crossover formation during meiosis

In most sexually reproducing organisms crossing over between chromosome homologs during meiosis is essential to produce 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 i...

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Bibliographic Details
Published in:	PLoS biology Vol. 21; no. 4; p. e3002085
Main Authors:	Gioia, Michael, Payero, Lisette, Salim, Sagar, Fajish V, Ghanim, Farnaz, Amamah F, Pannafino, Gianno, Chen, Jun Jie, Ajith, V P, Momoh, Sherikat, Scotland, Michelle, Raghavan, Vandana, Manhart, Carol M, Shinohara, Akira, Nishant, K T, Alani, Eric
Format:	Journal Article
Language:	English
Published:	United States Public Library of Science 20-04-2023 Public Library of Science (PLoS)
Subjects:	Analysis Biology and Life Sciences Chromosomes Cloning Crossing Over, Genetic Crystal structure Defects Deoxyribonucleic acid DNA DNA Breaks, Single-Stranded DNA, Cruciform Endonuclease Flap Endonucleases - genetics Flap Endonucleases - metabolism Gametes Genomes Identification and classification Intermediates Meiosis Meiosis - genetics Mismatch repair MLH1 protein Mutants Nuclease Nucleases Properties Proteins Reproduction (biology) Research and Analysis Methods Saccharomyces cerevisiae - genetics Saccharomyces cerevisiae - metabolism Saccharomyces cerevisiae Proteins - genetics Saccharomyces cerevisiae Proteins - metabolism Structural members Yeast Yeasts United States
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Summary:	In most sexually reproducing organisms crossing over between chromosome homologs during meiosis is essential to produce 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 of Rad2/XPG family nuclease Exo1 and the Mlh1-Mlh3 mismatch repair endonuclease. Here, we provide genetic evidence in baker's yeast that Exo1 promotes meiotic crossing over by protecting DNA nicks from ligation. We found that structural elements in Exo1 that interact with DNA, such as those required for the 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 reduced the crossover levels of exo1 DNA-binding mutants to levels that approached the exo1 null. In addition, our work identified a role for Exo1 in crossover interference. Together, these studies provide experimental evidence for Exo1-protected nicks being critical for the formation of meiotic crossovers and their distribution.
Bibliography:	new_version ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 The authors have declared that no competing interests exist.
ISSN:	1545-7885 1544-9173 1545-7885
DOI:	10.1371/journal.pbio.3002085