MIG1-DEPENDENT AND MIG1-INDEPENDENT GLUCOSE REGULATION OF MAL GENE-EXPRESSION IN SACCHAROMYCES-CEREVISIAE

Glucose repression is a global regulatory system in Saccharomyces cere visiae controlling carbon-source utilization, mitochondrial biogenesis gluconeogenesis and other metabolic pathways. Mig1p, a zinc-finger cl ass of DNA-binding protein, is a transcriptional repressor regulating GAL and SUC gene expression in response to glucose. This report demons trates that Mig1 protein represses transcription of the MAL61 and MAL6 2 structural genes and also the MAL63 gene, which encodes the Mal-acti vator. Mig1p DNA-binding sites were identified upstream of all three M AL genes. Both of the Mig1p-binding sites found in the bidirectional M AL61-MAL62 promoter were shown to function in the Mig1p-dependent gluc ose repression. Studies using constitutive Mal-activator alleles sugge st that glucose regulation of inducer availability is a second major c ontributing factor in glucose repression of MAL gene expression; and i s; even stronger than thp Mig1p-dependent component of repression. Mor eover, our results also suggest the contribution of other minor mechan isms in glucose regulation of MAL gene expression.