Structure and expression of the SNF1 gene of Saccharomyces cerevisiae

The SNF1 gene of Saccharomyces cerevisiae is essential for normal regulation of gene expression by glucose repression. A functional SNF1 gene product is required to derepress many glucose-repressible genes in response to conditions of low external glucose. In the case of the SUC2 structural gene for invertase, SNF1 acts at the RNA level. We have reported the isolation of a cloned gene that complements the snf1 defect in S. cerevisiae and that is homologous to DNA at the SNF1 locus (J. L. Celenza and M. Carlson, Mol. Cell. Biol. 4:49-53, 1984). In this work we identified a 2.4-kilobase polyadenylate-containing RNA encoded by the SNF1 gene and showed that its level is neither regulated by glucose repression nor dependent on a functional SNF1 product. The position of the SNF1 RNA relative to the cloned DNA was mapped, and the direction of transcription was determined. The cloned DNA was used to disrupt the SNF1 gene at its chromosomal locus. Gene disruption resulted in A Snf1- phenotype, thereby proving that the cloned gene is the SNF1 gene and showing that the phenotype of a true null mutation is indistinguishable from that of previously isolated snf1 mutations.