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Mol. Cell. Biol., Feb 1996, 669-676, Vol 16, No. 2
X Shi, A Finkelstein, AJ Wolf, PA Wade, ZF Burton and JA Jaehning
Regulated transcription initiation requires, in addition to RNA polymerase
II and the general transcription factors, accessory factors termed
mediators or adapters. We have used affinity chromatography to identify a
collection of factors that associate with Saccharomyces cerevisiae RNA
polymerase II (P. A. Wade, W. Werel, R. C. Fentzke, N. E. Thompson, J. F.
Leykam, R. R. Burgess, J. A. Jaehning, and Z. F. Burton, submitted for
publication). Here we report identification and characterization of a gene
encoding one of these factors, PAF1 (for RNA polymerase-associated factor
1). PAF1 encodes a novel, highly charged protein of 445 amino acids.
Disruption of PAF1 in S. cerevisiae leads to pleiotropic phenotypic traits,
including slow growth, temperature sensitivity, and abnormal cell
morphology. Consistent with a possible role in transcription, Paf1p is
localized to the nucleus. By comparing the abundances of many yeast
transcripts in isogenic wild-type and paf1 mutant strains, we have
identified genes whose expression is affected by PAF1. In particular,
disruption of PAF1 decreases the induction of the galactose-regulated genes
three- to fivefold. In contrast, the transcript level of MAK16, an
essential gene involved in cell cycle regulation, is greatly increased in
the paf1 mutant strain. Paf1p may therefore be required for both positive
and negative regulation of subsets of yeast genes. Like Paf1p, the GAL11
gene product is found associated with RNA polymerase II and is required for
regulated expression of many yeast genes including those controlled by
galactose. We have found that a gal11 paf1 double mutant has a much more
severe growth defect than either of the single mutants, indicating that
these two proteins may function in parallel pathways to communicate signals
from regulatory factors to RNA polymerase II.
Copyright © 1996, American Society for Microbiology
Paf1p, an RNA polymerase II-associated factor in Saccharomyces cerevisiae, may have both positive and negative roles in transcription
Department of Biochemistry, Biophysics and Genetics, University of Colorado Health Sciences Center, Denver 80262, USA.
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