McBroom L D, Sadowski P D
Department of Molecular and Medical Genetics, University of Toronto, Canada.
Curr Genet. 1995 Jun;28(1):1-11. doi: 10.1007/BF00311875.
Cell type in the yeast Saccharomyces cerevisiae is determined by information present at the MAT locus. Cells can switch mating types when cell-type information located at a silent locus, HML or HMR, is transposed to the MAT locus. The HML and HMR loci are kept silent through the action of a number of proteins, one of which is the DNA-binding protein, ABF1. We have identified a binding site for ABF1 within the Ya region of MATa and HMRa. In order to examine the function of this ABF1-binding site, we have constructed strains that lack the site in the MATa or HMRa loci. Consistent with the idea that ABF1 plays a redundant role in silencing, it was found that a triple deletion of the ABF1-binding sites at HMRE, Ya and I did not permit the expression of HMRa. We have also shown that chromosomal deletion of the binding site at MATYa had no effect on the level of cutting by the HO endonuclease nor on the amount of mating-type switching observed. Similarly, chromosomal deletion of all three ABF1-binding sites at HMRa had no effect on the directionality of mating-type switching.
酿酒酵母中的细胞类型由位于MAT基因座的信息决定。当位于沉默基因座HML或HMR的细胞类型信息转座到MAT基因座时，细胞可以转换交配类型。HML和HMR基因座通过多种蛋白质的作用保持沉默，其中一种是DNA结合蛋白ABF1。我们在MATa和HMRa的Ya区域内鉴定出了ABF1的一个结合位点。为了研究这个ABF1结合位点的功能，我们构建了在MATa或HMRa基因座中缺少该位点的菌株。与ABF1在沉默中起冗余作用的观点一致，发现HMRE、Ya和I处的ABF1结合位点三重缺失不允许HMRa表达。我们还表明，MATYa处结合位点的染色体缺失对HO内切核酸酶的切割水平或观察到的交配类型转换量没有影响。同样，HMRa处所有三个ABF1结合位点的染色体缺失对交配类型转换的方向性没有影响。
