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Multiple bHLH proteins regulate CIT2 expression in Saccharomyces cerevisiae
Author(s) -
Chen Linan,
Lopes John M.
Publication year - 2010
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.1757
Subject(s) - biology , saccharomyces cerevisiae , gene , basic helix loop helix , transcription factor , gene expression , reporter gene , psychological repression , two hybrid screening , genetics , regulation of gene expression , microbiology and biotechnology , dna binding protein
The basic helix–loop–helix (bHLH) proteins comprise a eukaryotic transcription factor family involved in multiple biological processes. They have the ability to form multiple dimer combinations and most of them also bind a 6 bp site (E‐box) with limited specificity. These properties make them ideal for combinatorial regulation of gene expression. The Saccharomyces cerevisiae CIT2 gene, which encodes citrate synthase, was previously known to be induced by the bHLH proteins Rtg1p and Rtg3p in response to mitochondrial damage. Rtg1p–Rtg3p dimers bind two R‐boxes (modified E‐boxes) in the CIT2 promoter. The current study tested the ability of all nine S. cerevisiae bHLH proteins to regulate the CIT2 gene. The results showed that expression of CIT2–lacZ reporter was induced in a ρ 0 strain by the presence of inositol via the Ino2p and Ino4p bHLH proteins, which are known regulators of phospholipid synthesis. Promoter mutations revealed that inositol induction required a distal E‐box in the CIT2 promoter. Interestingly, deleting the INO2, INO4 genes or the cognate E‐box revealed phosphate induction of CIT2 expression. This layer of expression required the two R‐boxes and the Pho4p bHLH protein, which is known to be required for phosphate‐specific regulation. Lastly, the data show that the Hms1p and Sgc1p bHLH proteins also play important roles in repression of CIT2–lacZ expression. Collectively, these results support the model that yeast bHLH proteins coordinate different biological pathways. Copyright © 2010 John Wiley & Sons, Ltd.