The RNA Polymerase II General Transcription Factors: Past, Present, and Future

RNA synthesis is a multistep process. The steps of thetranscription cycle were first dissected in studies usingthe bacterial RNA polymerase (RNAP) (Chamberlin1974; McClure 1985) and have recently been extended tothe eukaryotic RNAP systems. Transcription requiresthat RNAP associate with the promoter region and form astable initiation complex. In eukaryotes, this is accomplished with the aid of a set of auxiliary factors that aredifferent for each RNAP transcription system (i.e.,RNAPI, -II and -III; for review, see Zawel and Reinberg1995). Transcription by RNAPII minimally requires sixfactors (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH)termed the general transcription factors (GTFs). Stableassociation of RNAPII with promoter sequences requiresTFIID (or TBP), TFIIB, and TFIIF (for review, see Orphanides et al. 1996). However, the RNAPII transcriptionsystem is unique in that after the polymerase has stablyassociated with promoter sequences, two additional factors, TFIIE and TFIIH, are necessary for transcription(Flores et al. 1990; for review, see Drapkin and Reinberg1994; Orphanides et al. 1996). This is perhaps related toa unique structure found at the carboxyl terminus of thelargest subunit of RNAPII known as the carboxy-terminal domain (CTD) (Koleske and Young 1995; Dahmus1996)...