Whole Cell Extract

Most human genes are loaded with promoter proximally paused RNA polymerase II (RNAP II) molecules that are poised for release into productive elongation by P-TEFb. Gdown1, a protein that renders RNAP II responsive to mediator, is involved in RNAP II elongation control. During in vitro transcription assays Gdown1 specifically blocked elongation stimulation by TFIIF, inhibited the termination activity of TTF2, and influenced pausing factors NELF and DSIF, but did not affect the function of TFIIS or the mRNA capping enzyme. Without P-TEFb, Gdown1 led to the production of stably paused polymerases in the presence of nuclear extract. ChIP-Seq data demonstrated that Gdown1 mapped over essentially all poised polymerases across the human genome. Gdown1 increases the stability of poised polymerases while maintaining their responsiveness to P-TEFb, and mediator overcomes a Gdown1-mediated block of initiation by allowing TFIIF function. 1 whole cell extract sample in human HeLa cell. See associated publication.