Requirement of the carboxy-terminal domain of RNA polymerase II for the transcriptional activation of chromosomal c-fos and hsp70A genes

The carboxy-terminal domain of the large subunit of mouse and human RNA polymerase II contains 52 repeats of a heptapeptide which are the targets for a variety of kinases. We have used an α-amanitin resistant form of the large subunit of pol II to study the role of the carboxy-terminal domain in the expression of chromosomal genes. The large subunit of RNA polymerase II and deletion mutants thereof, which contain only 31 (LSΔ31) and 5 (LSΔ5) repeats, were expressed in 293 cells. Subsequently, the endogenous large subunit of RNA polymerase II was inhibited by α-amanitin and the induction of chromosomal c- fos and hsp70A genes was determined. Cells expressing the large subunit of RNA polymerase II and LSΔ31 were able to transcribe the c- fos and hsp70A genes after treatment with the phorbolester TPA and after heat-shock, respectively. In contrast, cells expressing LSΔ5 failed to induce expression of both genes.