Open AccessDecreased Meiotic Intergenic Recombination and Increased Meiosis I Nondisjunction in exo1 Mutants of Saccharomyces cerevisiae
Author(s) -
David T. Kirkpatrick,
John R. Ferguson,
Thomas D. Petes,
Lorraine S. Symington
Publication year - 2000
Publication title -
genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.792
H-Index - 246
eISSN - 1943-2631
pISSN - 0016-6731
DOI - 10.1093/genetics/156.4.1549
Subject(s) - biology , genetics , meiosis , nondisjunction , homologous recombination , saccharomyces cerevisiae , heteroduplex , chromosomal crossover , mitotic crossover , genetic recombination , schizosaccharomyces pombe , schizosaccharomyces , homologous chromosome , meiosis ii , dna , gene , recombination , chromosome , aneuploidy
Exonuclease I was originally identified as a 5' --> 3' deoxyribonuclease present in fractionated extracts of Schizosaccharomyces pombe and Saccharomyces cerevisiae. Genetic analysis of exo1 mutants of both yeasts revealed no major defect in meiosis, suggesting that exonuclease I is unlikely to be the primary activity that processes meiosis-specific double-strand breaks (DSBs). We report here that exo1 mutants of S. cerevisiae exhibit subtle but complex defects in meiosis. Diploids containing a homozygous deletion of EXO1 show decreased spore viability associated with an increase in meiosis I nondisjunction, while intergenic recombination is reduced about twofold. Exo1p functions in the same pathway as Msh5p for intergenic recombination. The length of heteroduplex tracts within the HIS4 gene is unaffected by the exo1 mutation. These results suggest that Exo1p is unlikely to play a major role in processing DSBs to form single-stranded tails at HIS4, but instead appears to promote crossing over to ensure disjunction of homologous chromosomes. In addition, our data indicate that exonuclease I may have a minor role in the correction of large DNA mismatches that occur in heteroduplex DNA during meiotic recombination at the HIS4 locus.