Kuchin S, Treich I, Carlson M
Department of Genetics and Development and Department of Microbiology, Columbia University, New York, NY 10032, USA.
Proc Natl Acad Sci U S A. 2000 Jul 5;97(14):7916-20. doi: 10.1073/pnas.140109897.
RNA polymerase II holoenzymes respond to activators and repressors that are regulated by signaling pathways. Here we present evidence for a "shortcut" mechanism in which the Snf1 protein kinase of the glucose signaling pathway directly regulates transcription by the yeast holoenzyme. In response to glucose limitation, the Snf1 kinase stimulates transcription by holoenzyme that has been artificially recruited to a reporter by a LexA fusion to a holoenzyme component. We show that Snf1 interacts physically with the Srb/mediator proteins of the holoenzyme in both two-hybrid and coimmunoprecipitation assays. We also show that a catalytically hyperactive Snf1, when bound to a promoter as a LexA fusion protein, activates transcription in a glucose-regulated manner; moreover, this activation depends on the integrity of the Srb/mediator complex. These results suggest that direct regulatory interactions between signal transduction pathways and RNA polymerase II holoenzyme provide a mechanism for transcriptional control in response to important signals.
RNA聚合酶II全酶对由信号通路调控的激活因子和抑制因子作出反应。在此，我们提供了一种“捷径”机制的证据，即葡萄糖信号通路的Snf1蛋白激酶通过酵母全酶直接调控转录。响应葡萄糖限制，Snf1激酶刺激全酶的转录，该全酶已通过LexA与全酶组分的融合被人工招募到一个报告基因上。我们表明，在双杂交和共免疫沉淀试验中，Snf1与全酶的Srb/中介蛋白发生物理相互作用。我们还表明，当作为LexA融合蛋白与启动子结合时，具有催化活性的Snf1以葡萄糖调节的方式激活转录；此外，这种激活依赖于Srb/中介复合体的完整性。这些结果表明，信号转导通路与RNA聚合酶II全酶之间的直接调控相互作用为响应重要信号的转录控制提供了一种机制。
