Role of RNA Polymerase II Carboxy-terminal Domain in Coordinating Transcription with RNA Processing

Abstract

The largest subunit of RNA polymerase II (pol II) hasan unusual structure at its carboxyl terminus comprisinga repeated heptad motif. This carboxy-terminal domain(CTD) has up to 52 copies of the heptad whose consensussequence (YSPTSPS) is completely conserved betweenfungi and vertebrates (Allison et al. 1985; Corden et al.1985). Although the largest subunits of pol I, pol II, andpol III are members of the same family which includesthe B′ and A′ subunits of eubacterial and archaeal RNApolymerases, the CTD is unique to pol II. The function ofthe CTD has been the object of intense speculation (Corden and Ingles 1992). It is required for cell viability andfor transcriptional activation of some genes in buddingyeast and mammalian cells (Nonet et al. 1987; Bartolomei et al. 1988; Scafe et al. 1990; Gerber et al. 1995),but paradoxically, it is dispensable for transcription fromthe adenovirus major late promoter in vitro. Recent observations have unexpectedly implicated the CTD notonly in synthesis of the primary transcript, but also in theRNA processing events that are uniquely directed to polII transcripts...