The RNA Polymerase-associated Factor 1 Complex (Paf1C) Directly Increases the Elongation Rate of RNA Polymerase I and Is Required for Efficient Regulation of rRNA Synthesis

Yinfeng Zhang,Archer D Smith,Matthew B Renfrow,David A Schneider

doi:10.1074/jbc.m110.115220

Yinfeng Zhang, Archer D Smith + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m110.115220

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Abstract

The rate of ribosome synthesis is proportional to the rate of cell proliferation; thus, transcription of rRNA by RNA polymerase I (Pol I) is an important target for the regulation of this process. Most previous investigations into mechanisms that regulate the rate of ribosome synthesis have focused on the initiation step of transcription by Pol I; however, recent studies in yeast and mammals have identified factors that influence transcription elongation by Pol I. The RNA polymerase-associated factor 1 complex (Paf1C) is a transcription elongation factor with known roles in Pol II transcription. We previously identified a role for Paf1C in transcription elongation by Pol I. In this study, genetic interactions between genes for Paf1C and Pol I subunits confirm this conclusion. In vitro studies demonstrate that purified Paf1C directly increases the rate of transcription elongation by Pol I. Finally, we show that Paf1C function is required for efficient control of Pol I transcription in response to target of rapamycin (TOR) signaling or amino acid limitation. These studies demonstrate that Paf1C plays an important direct role in cellular control of rRNA expression.

Highlights

Account for observed changes in the rate of rRNA transcription (3).we and others have postulated that the elongation rate of polymerase I (Pol I) transcription is regulated in response to growth conditions (6, 7)
Genetic Interactions Confirm a Role for polymerase-associated factor 1 complex (Paf1C) in Pol I Transcription—Pol I consists of 14 subunits; four of these subunits (A49, A34, A14, and A12) are not essential for growth
Growth of the double mutant strains was worse than the additive growth defects of the individual parental mutants (Fig. 1B).The simplest interpretation of this synthetic growth defect is that PAF1 and CTR9 are required for efficient Pol I transcription

Summary

Introduction

Account for observed changes in the rate of rRNA transcription (3).we and others have postulated that the elongation rate of Pol I transcription is regulated in response to growth conditions (6, 7). These data demonstrate that Paf1C directly enhances the rate of transcription elongation by Pol I and serves as an important regulator of rRNA synthesis. Unlike in the paf1⌬ strain, Pol I transcription remained responsive to rapamycin treatment in WT cells grown in ethanol (Fig. 3A).

Results

Conclusion