Mylin L M, Bushman V L, Long R M, Yu X, Lebo C M, Blank T E, Hopper J E
Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey 17033.
Genetics. 1994 Jul;137(3):689-700. doi: 10.1093/genetics/137.3.689.
The yeast Snf1p kinase is required for normal expression of many genes involved in utilization of non-glucose carbon. Snf1p is known to associate with several proteins. One is Sip1p, a protein that becomes phosphorylated in the presence of Snf1p and thus is a candidate Snf1p kinase substrate. We have isolated the SIP1 gene as a multicopy suppressor of the gal83-associated defect in glucose repression of GAL gene expression. Multicopy SIP1 also suppressed the gal82-associated defect in glucose repression, suggesting that SIP1, GAL83 and GAL82 function interdependently. Multicopy SIP1 gene reduces GAL1, GAL2, GAL7 and GAL10 gene expression three- to fourfold in cells grown in the presence of glucose but has no effect in cells grown on nonrepressing carbon. Sip1-deletion cells exhibited a two- to threefold increase in GAL gene expression compared to wild-type cells when grown on glucose. These studies show that SIP1 is a catabolite repression-specific negative regulator of GAL gene expression. Northern analysis revealed two SIP1 transcripts whose relative abundance changed with carbon source. Western blots revealed that Sip1p abundance is not markedly affected by carbon source, suggesting that Sip1p may be regulated post-translationally.
酵母Snf1p激酶是许多参与非葡萄糖碳利用的基因正常表达所必需的。已知Snf1p与几种蛋白质相关联。其中一种是Sip1p，一种在Snf1p存在下会发生磷酸化的蛋白质，因此是Snf1p激酶底物的候选者。我们已将SIP1基因分离出来，作为GAL基因表达的葡萄糖阻遏中与gal83相关缺陷的多拷贝抑制子。多拷贝SIP1也抑制了葡萄糖阻遏中与gal82相关的缺陷，这表明SIP1、GAL83和GAL82相互依赖发挥作用。在葡萄糖存在下生长的细胞中，多拷贝SIP1基因使GAL1、GAL2、GAL7和GAL10基因的表达降低三到四倍，但在以非阻遏性碳源生长的细胞中则没有影响。与野生型细胞相比，缺失Sip1的细胞在葡萄糖上生长时，GAL基因的表达增加了两到三倍。这些研究表明，SIP1是GAL基因表达的一种碳分解代谢物阻遏特异性负调节因子。Northern分析揭示了两种SIP1转录本，其相对丰度随碳源而变化。Western印迹显示，Sip1p的丰度不受碳源的显著影响，这表明Sip1p可能在翻译后受到调节。
