Transcriptional Regulation by Lge1p Requires a Function Independent of Its Role in Histone H2B Ubiquitination

Xiaoting Zhang,Ania Kolaczkowska,Frédéric Devaux,Sneh Lata Panwar,Timothy C Hallstrom,Claude Jacq,W Scott Moye-Rowley

doi:10.1074/jbc.m408333200

Abstract

Saccharomyces cerevisiae cells that have lost their mitochondrial genome (rho(0)) strongly induce transcription of multidrug resistance genes, including the ATP-binding cassette transporter gene PDR5. PDR5 induction in rho(0) cells requires the presence of the zinc cluster transcription factor Pdr3p. The PDR3 gene is positively autoregulated in rho(0) cells by virtue of the presence of two binding sites for Pdr3p in its promoter. We identify the novel protein Lge1p as a required participant in the rho(0) activation of PDR3 and PDR5 expression. Lge1p is a nuclear protein that has been found to play a role in ubiquitination of histone H2B at Lys(123). This ubiquitination requires the presence of the ubiquitin-conjugating enzyme Rad6p and the ubiquitin ligase Bre1p. Interestingly, rho(0) strains lacking Lge1p failed to induce PDR3 transcription, but induction was still seen in Deltarad6, Deltabre1, and H2B-K123R mutant strains. Microarray experiments also confirmed that the pattern of gene expression changes seen in cells lacking Lge1p, Bre1p, or Rad6p or containing the H2B-K123R mutant as the only form of H2B share some overlap but are distinct. These findings provide a strong argument that Lge1p has roles in gene regulation independent of its participation in the Rad6p-dependent ubiquitination of H2B.

Highlights

Saccharomyces cerevisiae cells that have lost their mitochondrial genome (␳0) strongly induce transcription of multidrug resistance genes, including the ATP-binding cassette transporter gene PDR5
Genetic Screen for Regulators of Retrograde Control of Pdr3p Activity—We have previously found that expression of the multidrug-resistant ABC transporter gene PDR5 is strongly induced in cells that have lost their mitochondrial genomic DNA (␳0) [21] or that have defects in biogenesis of the F0 component of the mitochondrial ATPase [23]
This mitochondrial dysfunction leads to activation of the zinc cluster transcription factor Pdr3p, which in turn positively autoregulates PDR3 gene expression

Summary

Introduction

Saccharomyces cerevisiae cells that have lost their mitochondrial genome (␳0) strongly induce transcription of multidrug resistance genes, including the ATP-binding cassette transporter gene PDR5. Microarray experiments confirmed that the pattern of gene expression changes seen in cells lacking Lge1p, Bre1p, or Rad6p or containing the H2B-K123R mutant as the only form of H2B share some overlap but are distinct. These findings provide a strong argument that Lge1p has roles in gene regulation independent of its participation in the Rad6p-dependent ubiquitination of H2B. Microarray experiments have indicated that PDR5 is one of the most highly induced genes upon activation of the Pdr pathway [20]

Methods

Results

Conclusion