Nishida Yuri, Ono Bun-ichiro
Frontier Doctoral Program in Science and Engineering, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu 525-8577, Shiga, Japan.
Yeast. 2007 Sep;24(9):723-30. doi: 10.1002/yea.1507.
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.
酿酒酵母的sir4 - 11菌株（sir4 - 11 HMLα MATα HMRa，非交配型）与a交配型菌株（SIR(+) HMLα MATa HMRa）杂交，形成二倍体克隆的频率为5×10⁻⁶，但获得的二倍体克隆通常（>70%）具有改变形式的含HMRa的限制性片段，称为“@HMRa”。我们之前发现一些“@HMRa”与HMRa向HMRα的转变有关。在本报告中，我们提供证据表明另一种“@HMRa”与Ty插入HMR的Ya有关。我们还发现，通过紫外线照射，sir4 - 11菌株的交配频率提高到9×10⁻⁴的水平，并且通过破坏sir4 - 11菌株的RAD52完全阻止了“@HMRa”的产生。因此，我们得出结论，导致“@HMRa”产生的突变在sir4 - 11菌株交配之前就已发生。由于这些突变，sir4 - 11菌株转变为α交配型，并易于与a交配型菌株交配。我们讨论了sir4 - 11菌株在研究酿酒酵母HMR基因座突变方面的用途。
