The role of Exo1p exonuclease in DNA end resection to generate gene conversion tracts in Saccharomyces cerevisiae.
Bottom Line: In accordance with this expectation, gene conversion tract lengths associated with spontaneous crossovers in exo1 strains were reduced about twofold relative to wild type.For UV-induced events, conversion tract lengths associated with crossovers were also shorter for the exo1 strain than for the wild-type strain (3.2 and 7.6 kb, respectively).Unexpectedly, however, the lengths of conversion tracts that were unassociated with crossovers were longer in the exo1 strain than in the wild-type strain (6.2 and 4.8 kb, respectively).
Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina 27710.Show MeSH
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Mentions: To distinguish among the patterns of LOH shown in Figure 1 and to map the positions of the LOH, we used diploids generated by crossing two sequence-diverged haploids, W303a and YJM789 (St. Charles and Petes 2013; Yin and Petes 2013). This diploid, in addition to being heterozygous for SNPs located throughout the genome, contained markers on either chromosome V (YYy29.8) or chromosome IV (YYy34) that allowed identification of reciprocal crossovers (Figure 2). The diploids are homozygous for ade2-1, an ochre mutation. In the presence of zero, one, and two copies of the ochre suppressor SUP4-o, the diploids form red, pink, and white colonies, respectively (Barbera and Petes 2006). The SUP4-o gene is integrated near the telomeres of chromosomes V (YYy29.8) and IV (YYy34) in the strains used in our study. In these diploids, crossovers between the centromere and the heterozygous SUP-o marker produce red/white sectored colonies. Only half of the crossover events are detectable by this system (Chua and Jinks-Robertson 1991), since cosegregation of two recombined chromosomes into one daughter cell and two unrecombined chromosomes into the other daughter does not lead to LOH.
Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina 27710.