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Eukaryotic Cell, May 2007, p. 786-796, Vol. 6, No. 5
1535-9778/07/$08.00+0     doi:10.1128/EC.00383-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Multiple Basic Helix-Loop-Helix Proteins Regulate Expression of the ENO1 Gene of Saccharomyces cerevisiae{triangledown}

Meng Chen and John M. Lopes*

Department of Biological Sciences, Wayne State University, Detroit, Michigan

Received 5 December 2006/ Accepted 1 March 2007

The basic helix-loop-helix (bHLH) eukaryotic transcription factors have the ability to form multiple dimer combinations. This property, together with limited DNA-binding specificity for the E box (CANNTG), makes them ideally suited for combinatorial control of gene expression. We tested the ability of all nine Saccharomyces cerevisiae bHLH proteins to regulate the enolase-encoding gene ENO1. ENO1 was known to be activated by the bHLH protein Sgc1p. Here we show that expression of an ENO1-lacZ reporter was also regulated by the other eight bHLH proteins, namely, Ino2p, Ino4p, Cbf1p, Rtg1p, Rtg3p, Pho4p, Hms1p, and Ygr290wp. ENO1-lacZ expression was also repressed by growth in inositol-choline-containing medium. Epistatic analysis and chromatin immunoprecipitation experiments showed that regulation by Sgc1p, Ino2p, Ino4p, and Cbf1p and repression by inositol-choline required three distal E boxes, E1, E2, and E3. The pattern of bHLH binding to the three E boxes and experiments with two dominant-negative mutant alleles of INO4 and INO2 support the model that bHLH dimer selection affects ENO1-lacZ expression. These results support the general model that bHLH proteins can coordinate different biological pathways via multiple mechanisms.

* Corresponding author. Mailing address: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202. Phone: (313) 993-7816. Fax: (313) 577-6891. E-mail: jlopes{at}sun.science.wayne.edu

{triangledown} Published ahead of print on 9 March 2007.

Eukaryotic Cell, May 2007, p. 786-796, Vol. 6, No. 5
1535-9778/07/$08.00+0     doi:10.1128/EC.00383-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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