Carrico P M, Zitomer R S
Department of Biological Sciences, University at Albany/State University of New York, 12222, USA.
Genetics. 1998 Feb;148(2):637-44. doi: 10.1093/genetics/148.2.637.
The Tup1 and Ssn6 proteins of Saccharomyces cerevisiae form a general transcriptional repression complex that regulates the expression of a diverse set of genes including aerobically repressed hypoxic genes, a-mating type genes, glucose repressed genes, and genes controlling cell flocculence. To identify amino acid residues in the Tup1 protein that are required for repression function, we selected for mutations that derepressed the hypoxic genes. Three missense mutations that accumulated stable protein were isolated, and an additional three were generated by site-directed mutagenesis. The mutant protein L62R was unable to complex with Ssn6 or repress expression of reporter genes for the hypoxic and glucose repressed regulons or the flocculence phenotype, however, expression of the a-mating type reporter gene was still repressed. The remaining mutations fell within the WD repeat region of Tup1. These mutations had different effects on the expression of the four Tup1 repressed regulons assayed, indicating that the WD repeats serve different roles for repression of different regulons.
酿酒酵母的Tup1和Ssn6蛋白形成一个通用转录抑制复合体，该复合体调控多种基因的表达，包括需氧抑制的缺氧基因、α-交配型基因、葡萄糖抑制基因以及控制细胞絮凝的基因。为了鉴定Tup1蛋白中抑制功能所需的氨基酸残基，我们筛选了能解除缺氧基因抑制的突变。分离出三个积累稳定蛋白的错义突变，并通过定点诱变产生了另外三个突变。突变蛋白L62R无法与Ssn6形成复合体，也不能抑制缺氧和葡萄糖抑制调节子的报告基因表达或絮凝表型，然而，α-交配型报告基因的表达仍受到抑制。其余突变位于Tup1的WD重复区域内。这些突变对所检测的四个Tup1抑制调节子的表达有不同影响，表明WD重复在不同调节子的抑制中发挥不同作用。
