An experimental system for the study of mutations in the HMR locus of Saccharomyces cerevisiae: the insertion of Ty into HMRa vs. the conversion of HMRa to HMRalpha.
A cross between a sir4-11 strain (sir4-11 HMLalpha MATalpha HMRa, non-mating type) and an a-mating strain (SIR(+) HMLalpha MATa HMRa) of Saccharomyces cerevisiae forms diploid clones at a frequency of 5 x 10(-6), but the obtained diploid clones often (>70%) have altered forms of the HMRa-containing restriction fragment, designated @ HMRa'. We previously found that some HMRa's are associated with the conversion of HMRa to HMRalpha. In this report, we present evidence that another @ HMRa' associates with the insertion of Ty into Ya of HMR. We also found that the sir4-11 strain increased mating frequency by UV irradiation to a level of 9 x 10(-4), and that generation of HMRa' was completely prevented by disruption of RAD52 of the sir4-11 strain. Hence, we conclude that the mutations that cause generation of HMRa' occur in the sir4-11 strain prior to mating. Due to these mutations, the sir4-11 strain converts to alpha-mating type and readily mates with the a-mating strain. We discuss the usefulness of the sir4-11 strain for the study of mutations in the HMR locus of S. cerevisiae.
Nishida
Yuri
Y
Frontier Doctoral Program in Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu 525-8577, Shiga, Japan.
Ono
Bun-ichiro
B
D016386:Chromosome Walking; D004271:DNA, Fungal / Q000235:genetics; D049770:Genes, Mating Type, Fungal / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D016133:Polymerase Chain Reaction; D018626:Retroelements / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics*
D004271:DNA, Fungal; D018626:Retroelements; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae