Transcription regulation of the Saccharomyces cerevisiae PHO5 gene by the Ino2p and Ino4p basic helix-loop-helix proteins

Mol Microbiol. 2012 Jan;83(2):395-407. doi: 10.1111/j.1365-2958.2011.07941.x. Epub 2011 Dec 19.


The Saccharomyces cerevisiae PHO5 gene product accounts for a majority of the acid phosphatase activity. Its expression is induced by the basic helix-loop-helix (bHLH) protein, Pho4p, in response to phosphate depletion. Pho4p binds predominantly to two UAS elements (UASp1 at -356 and UASp2 at -247) in the PHO5 promoter. Previous studies from our lab have shown cross-regulation of different biological processes by bHLH proteins. This study tested the ability of all yeast bHLH proteins to regulate PHO5 expression and identified inositol-mediated regulation via the Ino2p/Ino4p bHLH proteins. Ino2p/Ino4p are known regulators of phospholipid biosynthetic genes. Genetic epistasis experiments showed that regulation by inositol required a third UAS site (UASp3 at -194). ChIP assays showed that Ino2p:Ino4p bind the PHO5 promoter and that this binding is dependent on Pho4p binding. These results demonstrate that phospholipid biosynthesis is co-ordinated with phosphate utilization via the bHLH proteins.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acid Phosphatase / biosynthesis*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Chromatin Immunoprecipitation
  • DNA, Fungal / metabolism
  • Enhancer Elements, Genetic
  • Gene Expression Regulation, Fungal*
  • Inositol / metabolism*
  • Models, Biological
  • Phospholipids / metabolism
  • Promoter Regions, Genetic
  • Protein Binding
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / biosynthesis*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Factors / metabolism*
  • Transcription, Genetic*


  • Basic Helix-Loop-Helix Transcription Factors
  • DNA, Fungal
  • INO2 protein, S cerevisiae
  • INO4 protein, S cerevisiae
  • Phospholipids
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Inositol
  • Acid Phosphatase
  • PHO5 protein, S cerevisiae