MIG1-dependent and MIG1-independent glucose regulation of MAL gene expression in Saccharomyces cerevisiae.

Glucose repression is a global regulatory system in Saccharomyces cerevisiae controlling carbon-source utilization, mitochondrial biogenesis, gluconeogenesis and other metabolic pathways. Mig1p, a zinc-finger class of DNA-binding protein, is a transcriptional repressor regulating GAL and SUC gene expression in response to glucose. This report demonstrates that Mig1 protein represses transcription of the MAL61 and MAL62 structural genes and also the MAL63 gene, which encodes the Mal-activator. Mig1p DNA-binding sites were identified upstream of all three MAL genes. Both of the Mig1p-binding sites found in the bidirectional MAL61-MAL62 promoter were shown to function in the Mig1p-dependent glucose repression. Studies using constitutive Mal-activator alleles suggest that glucose regulation of inducer availability is a second major contributing factor in glucose repression of MAL gene expression and is even stronger than the Mig1p-dependent component of repression. Moreover, our results also suggest the contribution of other minor mechanisms in glucose regulation of MAL gene expression.