Hirst M, Kobor M S, Kuriakose N, Greenblatt J, Sadowski I
Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
Mol Cell. 1999 May;3(5):673-8. doi: 10.1016/s1097-2765(00)80360-3.
Phosphorylation of the yeast transcription factor GAL4 at S699 is required for efficient galactose-inducible transcription. We demonstrate that this site is a substrate for the RNA polymerase holoenzyme-associated CDK SRB10. S699 phosphorylation requires SRB10 in vivo, and this site is phosphorylated by purified SRB10/ SRB11 CDK/cyclin in vitro. RNA Pol II holoenzymes purified from WT yeast phosphorylate GAL4 at sites observed in vivo whereas holoenzymes from srb10 yeast are incapable of phosphorylating GAL4 at S699. Mutations at GAL4 S699 and srb10 are epistatic for GAL induction, demonstrating that SRB10 regulates GAL4 activity through this phosphorylation in vivo. These results demonstrate a function for the SRB10/ CDK8 holoenzyme-associated CDK that involves regulation of transactivators by phosphorylation during transcriptional activation.
酵母转录因子GAL4在S699位点的磷酸化是高效半乳糖诱导转录所必需的。我们证明该位点是与RNA聚合酶全酶相关的CDK SRB10的底物。S699位点的磷酸化在体内需要SRB10，并且该位点在体外被纯化的SRB10/SRB11 CDK/细胞周期蛋白磷酸化。从野生型酵母中纯化的RNA Pol II全酶在体内观察到的位点使GAL4磷酸化，而来自srb10酵母的全酶不能在S699位点使GAL4磷酸化。GAL4 S699和srb10的突变对于GAL诱导是上位性的，表明SRB10在体内通过这种磷酸化调节GAL4活性。这些结果证明了与SRB10/CDK8全酶相关的CDK的功能，该功能涉及在转录激活过程中通过磷酸化调节反式激活因子。
