Livi G P, Hicks J B, Klar A J
Cold Spring Harbor Laboratory, New York 11724.
Mol Cell Biol. 1990 Jan;10(1):409-12. doi: 10.1128/mcb.10.1.409-412.1990.
The silent mating-type genes (HML and HMR) of Saccharomyces cerevisiae are kept under negative transcriptional control by the trans-acting products of the four MAR/SIR loci. MAR/SIR gene mutations result in the simultaneous derepression of HML and HMR gene expression. The sum1-1 mutation was previously identified as an extragenic suppressor of mutations in MAR1 (SIR2) and MAR2 (SIR3). As assayed genetically, sum1-1 is capable of restoring repression of silent mating-type information in cells containing mar1 or mar2 null mutations. We show here that the mating-type phenotype associated with sum1-1 results from a dramatic reduction in the steady-state level of HML and HMR gene transcripts. At the same time, the sum1-1 mutation has no significant effect on the level of each of the four MAR/SIR mRNAs.
酿酒酵母的沉默交配型基因（HML和HMR）受到四个MAR/SIR位点的反式作用产物的负转录调控。MAR/SIR基因突变导致HML和HMR基因表达同时去抑制。sum1-1突变先前被鉴定为MAR1（SIR2）和MAR2（SIR3）突变的基因外抑制子。通过遗传学分析，sum1-1能够恢复含有mar1或mar2无效突变的细胞中沉默交配型信息的抑制。我们在此表明，与sum1-1相关的交配型表型是由于HML和HMR基因转录本的稳态水平显著降低所致。同时，sum1-1突变对四个MAR/SIR mRNA中的每一个的水平没有显著影响。
