Multiple basic helix-loop-helix proteins regulate expression of the ENO1 gene of Saccharomyces cerevisiae.
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.
Chen
Meng
M
Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA.
Lopes
John M
JM
D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D024721:E-Box Elements / Q000235:genetics; D004843:Epistasis, Genetic; D019143:Evolution, Molecular; D015966:Gene Expression Regulation, Fungal; D005799:Genes, Dominant; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010751:Phosphopyruvate Hydratase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D001616:beta-Galactosidase / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D010751:Phosphopyruvate Hydratase; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D001616:beta-Galactosidase; C521376:ENO1 protein, S cerevisiae