Identification of a Decay in Transcription Potential That Results in Elongation Factor Dependence of RNA Polymerase II

Weigang Gu,Daniel Reines

doi:10.1074/jbc.270.19.11238

Abstract

The rate of RNA elongation by RNA polymerase II (pol II) is affected by DNA sequences called intrinsic arrest sites. Efficient transcription through these sites requires elongation factor SII. In addition to the sequence-specific features of the DNA, we show that the acquisition of SII-dependence is a function of its "dwell-time" at an arrest site. This temperature-dependent decay in elongation potential appears irreversible, implying that factor-dependent and factor-independent elongation complexes are not mutually interconvertible at this position. TFIIF and NH4Cl are known to increase the elongation rate of pol II. Both agents preempt arrest, consistent with the idea that elongation dwell time influences the process. TFIIF and SII act upon different steps in a complementary way to prevent or resolve arrest, respectively. They are probably instrumental in facilitating the efficient transcription of large eukaryotic genes in vivo.

Highlights

IntroductionThe rate of RNA elongation by RNA polymerase II (pol II) is affected by DNA sequences called intrinsic arrest sites
From the Graduate Program in Biochemistry & Molecular Biology and the Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322
Elongation is restricted by providing a limited subset of the four nucleoside triphosphates (NTPs), removing them, and repeating the process with the appropriate NTP(s) to assemble elongation complexes bearing sequentially larger RNA chains

Summary

Introduction

The rate of RNA elongation by RNA polymerase II (pol II) is affected by DNA sequences called intrinsic arrest sites. Efficient transcription through these sites requires elongation factor SII. They cannot extend pre-existing RNA chains, RNA release from the template is a terminal event in RNA synthesis (reviewed in Kane, 1994). At specific sites within genes, pol II becomes unable to continue chain elongation but does not release its nascent RNA This loss of elongation competence is referred to as arrest, the molecular mechanism of which is poorly understood.

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