An RNA polymerase II holoenzyme responsive to activators

Abstract

RNA polymerase II requires multiple general transcription factors to initiate site-specific transcription. These proteins can assemble in an ordered fashion onto promoter DNA in vitro, and such ordered assembly may occur in vivo (Fig. 1a). Some general transcription factors can interact with RNA polymerase II in the absence of DNA, however, suggesting that RNA polymerase II may also assemble into a multi-component complex containing a subset of initiation factors before binding to promoter DNA (Fig. 1b). Here we present evidence from the yeast Saccharomyces cerevisiae for such an RNA polymerase II holoenzyme, a multi-subunit complex containing roughly equimolar amounts of RNA polymerase II, a subset of general transcription factors, and SRB regulatory proteins. Transcription by this holoenzyme is stimulated by the activator protein GAL4-VP16, a feature not observed with purified RNA polymerase II and general transcription factors alone. We propose that the holoenzyme is a form of RNA polymerase II readily recruited to promoters in vivo.

Regulation of RNA polymerase II activity by CTD phosphorylation and cell cycle control

“…CDK8 (yeast SRB10) and its regulatory partner cyclin C (yeast SRB11) were initially isolated in yeast using a genetic screen for suppressors of truncation mutations in the RNAP II CTD (Koleske et al, 1992;Thompson et al, 1993;Koleske and Young, 1994;Liao et al, 1995). The CDK8-cyclin C complex was subsequently shown to be associated with the RNAP II holoenzyme in yeast (Liao et al, 1995) and in mammalian cells (Ossipow et al, 1995;Maldonado et al, 1996).…”

Transcriptional control and the role of silencers in transcriptional regulation in eukaryotes

“…then interacts directly with RNA pol IIa and subsequently recruits TFIIH to the C-terminal domain (CTD) of RNA pol IIa [42]. A large aggregate of proteins known as mediator, consisting of 20 or so proteins, including several suppressors of RNA polymerase B (II) proteins (' SRBs ') [43], then assemble at the CTD of RNA pol IIa [43][44][45].…”

“…More recently a large multisubunit complex known as RNA pol II holoenzyme, containing RNA pol II, TFIIB, TFIIH and mediator [53,54] has been identified that can assemble independently of a promoter [44,45]. The identification of RNA pol II holoenzyme that is capable of responding to enhancers [43] suggests a different model for transcription-apparatus assembly.…”

Multiple mammalian proteasomal ATPases, but not proteasome itself, are associated with TATA‐binding protein and a novel transcriptional activator, TIP120

“…5A). Yeast SUG1 has been shown to be a component of the 1200 kDa yeast RNA polymerase II holoenzyme, which contains TBP and other transcription factors (Thompson et al 1993;Koleske & Young 1994). Since some proteasomal ATPases have the ability to form heterodimers through their leucine zipper-like structures (Ohana et al 1993) various polypeptides are considered to interact with the ATPases.…”