A Novel RNA Polymerase II Complex Contains Cdc73p and Paf1p.

Cdc73p and Paf1p were identified as proteins associated with RNA polymerase II.¹ Paf1p is a nuclear protein important for normal cell growth and morphology, and induction of the GAL genes. ² Cdc73p is also nuclear and is required for growth at 38°C. Cdc73p forms a stable complex with RNA polymerase II in vitro, and CDC73 mutations are synthetically lethal with mutations in pol II in vivo (H. Klein, personal communication). To study pol II complexes containing Cdc73p and Paf1p, and to determine the relationship of these complexes to the "holoenzyme" ³, we used Cdc73p and Paf1p GST-tagged constructs to functionally replace the chromosomal copies of CDC73 and PAF1. Isolation of the tagged complexes revealed a form of pol II containing both Cdc73p and Paf1p, but lacking the Srbps found in the holoenzyme. Cdc73p and Paf1p are not present in the holoenzyme, suggesting that these two pol II complexes are distinct. A complex tagged on TFIIF (GST-Tfg2p) includes both Cdc73p/Paf1p and the Srbps confirming the coexistence of the two forms of RNA polymerase in yeast. The Cdc73p/Paf1p complex includes Gal11p, Sua7p (TFIIB), and Anc1p, but lacks TBP, TFIIS, and TFIIH. Applying the technique of differential display, we have identified several genes which require functional forms of Cdc73p and Paf1p for normal expression. ¹ Wade et al. Pro. Exp. Pur. in press. ² Shi et al. Mol. Cell. Biol. 1996 16:669-667. ³ Kim et al. Cell 1994 77:599-608; Koleske and Young 1994 Nature 368:466-469.