A functional requirement for the Saccharomyces cerevisiae Paf1 complex in RNA 3' end formation.
Kathryn E. Kumer, David M. Mauger, Karen M. Arndt
Biological Sciences, University of Pittsburgh, 4259 Fifth Ave., Pittsburgh, PA, 15260, U.S.A.
Transcription elongation is an important regulatory step in the RNA polymerase II (pol II) transcription cycle. Previous work from our laboratory and others strongly suggests that the Paf1 complex interacts with and regulates the activity of pol II during transcription elongation. To further investigate the function of the Paf1 complex in vivo, we performed a genetic study of the component Rtf1. Null mutations in RTF1 confer two phenotypes associated with defective transcription elongation, sensitivity to base analogs and the Spt- phenotype. To identify novel mutations in RTF1, we performed a genetic screen for rtf1 mutations that confer conditional mutant phenotypes. We identified three new rtf1 missense mutations. To identify proteins that functionally interact with the Paf1 complex, we performed a screen for multicopy suppressors of the rtf1 mutations. This screen identified NAB3 as a suppressor of rtf1. Nab3 interacts with the pol II-associated hnRNP Nrd1. Together, Nrd1 and Nab3 are required for efficient 3' end formation of certain nonpolyadenylated pol II transcripts, including snoRNAs. Using assays to detect transcriptional readthrough of snoRNA genes, we have shown that deletion of certain Paf1 complex members causes strong defects in snoRNA 3' end formation. By chromatin immunoprecipitation analysis, we have found that the Paf1 complex and Nab3 associate with snoRNA genes in vivo. We are testing whether the Paf1 complex regulates Nab3 association at these loci.
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