Kobayashi Yoshifumi, Inai Tomomi, Mizunuma Masaki, Okada Ichitaro, Shitamukai Atsunori, Hirata Dai, Miyakawa Tokichi
Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan.
Biochem Biophys Res Commun. 2008 Mar 28;368(1):50-5. doi: 10.1016/j.bbrc.2008.01.033. Epub 2008 Jan 15.
In the yeast Saccharomyces cerevisiae, Tup1, in association with Cyc8 (Ssn6), functions as a general transcriptional corepressor. This repression is mediated by recruitment of the Tup1-Cyc8 complex to target promoters through sequence-specific DNA-binding proteins such as Sko1, which mediates the HOG pathway-dependent regulation. We identified tup1 and cyc8 mutant alleles as the suppressor of osmo-sensitivity of the hog1Delta strain. In these mutants, although the expression of the genes under the control of DNA-binding proteins other than Sko1 was apparently normal, the Sko1-regulated genes GRE2 and AHP1 were derepressed under non-stress conditions, suggesting that the Tup1 and Cyc8 mutant proteins were specifically defective in the repression of the Sko1-dependent genes. Chromatin immunoprecipitation analyses of the GRE2 promoter in the mutants demonstrated that the Sko1-Tup1-Cyc8 complex was localized to the promoter, together with Gcn5/SAGA, suggesting that the erroneous recruitment of SAGA to the promoter led to the derepression.
在酿酒酵母中，Tup1与Cyc8（Ssn6）结合，作为一种通用的转录共抑制因子发挥作用。这种抑制作用是通过序列特异性DNA结合蛋白（如介导HOG途径依赖性调控的Sko1）将Tup1-Cyc8复合物募集到靶启动子上来介导的。我们鉴定出tup1和cyc8突变等位基因是hog1Delta菌株渗透敏感性的抑制因子。在这些突变体中，尽管除Sko1之外的DNA结合蛋白控制下的基因表达明显正常，但Sko1调控的基因GRE2和AHP1在非应激条件下被去抑制，这表明Tup1和Cyc8突变蛋白在抑制Sko1依赖性基因方面存在特异性缺陷。对突变体中GRE2启动子的染色质免疫沉淀分析表明，Sko1-Tup1-Cyc8复合物与Gcn5/SAGA一起定位于启动子，这表明SAGA错误募集到启动子导致了去抑制。
