A NOVEL COLLECTION OF ACCESSORY FACTORS ASSOCIATED WITH YEAST RNA-POLYMERASE-II

A relatively simple subset of general transcription factors is suffici ent for transcript initiation by RNA polymerase II. However, a recentl y identified '' holoenzyme '' contains additional accessory proteins r equired for mediating signals from some activators (Y-J. Kim et al., 1 994, Cell 77, 599-608; A. Koleske and R. Young, 1994, Nature 368, 466- 469), By immobilizing RNA polymerase II and associated proteins (RAPs) from a transcriptionally active yeast extract, we have identified a n ovel collection of proteins distinct from those found in the holoenzym e, The eluted RAP fraction did not contain the holoenzyme components S rb2,4,5 + 6p, Gal11p, or Sug1p, but did include the known transcriptio n factors TFIIB and TFIIS and the three subunits of yeast TFIIF (Ssu71 p/ Tfg1p, Tfg2p, and Anc1p/Tfg3p). Also isolated as RAPs are two prote ins (Cdc73p and Paf1p) with interesting connections to gene expression . Mutations in CDC73 and PAF1 affect cell growth and the abundance of transcripts from a subset of yeast genes (X. Shi et al., Mol. Cell. Bi ol., 1996 16, 669-676). The RAP fraction may therefore define one or m ore functional forms of RNA polymerase II distinct from the activator- mediating holoenzyme. (C) 1996 Academic Press, Inc.