Sub1 Functions in Osmoregulation and in Transcription by both RNA Polymerases II and III

Abstract

Sub1 is implicated in transcriptional activation, elongation, and mRNA 3′-end formation in budding yeast. To gain more insight into its function, we performed a synthetic genetic array screen with SUB1 that uncovered genetic interactions with genes involved in the high-osmolarity glycerol (HOG) osmoresponse pathway. We find that Sub1 and the HOG pathway are redundant for survival in moderate osmolarity. Chromatin immunoprecipitation analysis shows that Sub1 is recruited to osmoresponse gene promoters during osmotic shock and is required for full recruitment of TBP, TFIIB, and RNA polymerase II (RNAP II) at a subset of these genes. Furthermore, we detect Sub1 at the promoter of every constitutively transcribed RNAP II and, unexpectedly, at every RNAP III gene tested, but not at the RNAP I-transcribed ribosomal DNA promoter. Significantly, deletion of SUB1 reduced levels of promoter-associated RNAP II or III at these genes, but not TBP levels. Together these data suggest that, in addition to a general role in polymerase recruitment at constitutive RNAP II and RNAP III genes, during osmotic shock, Sub1 facilitates osmoresponse gene transcription by enhancing preinitiation complex formation.

SUPPLEMENTAL MATERIAL

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

ACKNOWLEDGMENTS

We thank Elizabeth Miller (Columbia University) and Jennifer Haynes and Brenda Andrews (University of Toronto) for strains and plasmids and Michael Hampsey (Robert Wood Johnson Medical School) for generously supplying the TFIIB antibody. We thank Patricia Richard for insightful discussions and for comments on the manuscript.

E. Rosonina is a Research Fellow of the Terry Fox Foundation through an award from the National Cancer Institute of Canada. This work was supported by grants from the National Institutes of Health to J.L.M. and I.M.W.