Multiple Yeast Genes, Including Paf1 Complex Genes, Affect Telomere Length via Telomerase RNA Abundance

Abstract

Twofold reductions in telomerase RNA levels cause telomere shortening in both humans and the yeast Saccharomyces cerevisiae. To test whether multiple genes that affect telomere length act by modulating telomerase RNA abundance, we used real-time reverse transcription-PCR to screen S. cerevisiae deletion strains reported to maintain shorter or longer telomeres to determine the levels of their telomerase RNA (TLC1) abundance. Of 290 strains screened, 5 had increased TLC1 levels; 4 of these maintained longer telomeres. Twenty strains had decreased TLC1 levels; 18 of these are known to maintain shorter telomeres. Four strains with decreased TLC1 RNA levels contained deletions of subunits of Paf1C (polymerase II-associated factor complex). While Paf1C had been implicated in the transcription of both polyadenylated and nonpolyadenylated RNAs, Paf1C had not been associated previously with the noncoding telomerase RNA. In Paf1C mutant strains, TLC1 overexpression partially rescues telomere length and cell growth defects, suggesting that telomerase RNA is a critical direct or indirect Paf1C target. Other factors newly identified as affecting TLC1 RNA levels include cyclin-dependent kinase, the mediator complex, protein phosphatase 2A, and ribosomal proteins L13B and S16A. This report establishes that a subset of telomere length genes act by modulating telomerase RNA abundance.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/ .

ACKNOWLEDGMENTS

We are grateful to Joan Betz and Judith Jaehning for the JJ Paf1C mutant strains and the pJJ1358 plasmid and to Timothy Hughes for the R1158 strain and the RP188 plasmid. David Whitcombe of DxS Limited generously designed the luciferase scorpion primer set. We also thank David Zappulla and Karen Goodrich for technical assistance and fruitful discussions.

A.D.M. was a Research Associate of the Howard Hughes Medical Institute.