Direct Pathway to RNA Polymerase II

Science's STKE  13 Jul 2004:
Vol. 2004, Issue 241, pp. tw252
DOI: 10.1126/stke.2412004tw252

Cellular responses to the extracellular environment can involve changes in gene expression, often the end point of signaling cascades that originate at the cell surface. Some signaling pathways regulate RNA polymerase II enzyme activity to control transcription. Many pathways impinge on transactivator proteins poised at gene promoters. These transactivators recruit the RNA polymerase II by interacting with regulator proteins of the Srb and Mediator complexes that also make up the polymerase holoenzyme. Chang et al. report that the Ras-protein kinase A (PKA) signaling pathway of the yeast Saccharomyces cerevisiae, which controls cell proliferation, targets the Srb9p protein in the Srb complex. Srb proteins and the Ras-PKA pathway are known to repress the expression of genes during the stationary phase of cell growth. Srb9p was phosphorylated by PKA in vitro and in vivo. Expression of a constitutively activated form of Ras also increased phosphorylation of Srb9p and the modification modulated the effect of the Srb complex on cell growth. The authors propose that by directly targeting proteins of the polymerase complex, cells could rapidly induce broad changes in gene expression.

Y.-W. Chang, S. C. Howard, P. K. Herman, The Ras/PKA signaling pathway directly targets the Srb9 protein, a component of the general RNA polymerase II transcription apparatus. Mol. Cell 15, 107-116 (2004). [Online Journal]