ASPP1 and ASPP2 are new transcriptional targets of E2F

The E2F family of transcription factors regulates the expression of a number of genes whose products are involved in cell cycle control, DNA replication and apoptosis. We show here that E2F-1 binds in vivo the promoters of ASPP1 and ASPP2 genes, two activators of p53-mediated apoptosis, E2F-1, E2F-2 and E2F-3 all activate the isolated ASPP1 and ASPP2 promoters. Overexpression or deregulation of E2F-1 increased the expression levels of ASPP1 and ASPP2 mRNA and proteins. The identification of ASPP1 and ASPP2 genes as transcriptional targets of E2F provides another mechanism by which E2F cooperates with p53 to induce apoptosis.

Genetic aspects of carbon catabolite repression of the STA2 glucoamylase gene in Saccharomyces cerevisiae

Three regulatory genes, known to be required for glucose repression/derepression of some genes in Saccharomyces cerevisiae, were disrupted to study their effects on the carbon-source regulation of the STA2 glucoamylase gene expression. Using a STA2-lacZ fusion it was found that: (1) the MIG1 gene is dispensable for the repression of the STA2 gene; (2) there are two components in the carbon-source repression of STA2: HXK2-dependent and HXK2-independent; and (3) the HAP2 gene seems to be involved in repression rather than activation of the STA2 expression.

Genes required for derepression of an extracellular glucoamylase gene, STA2, in the yeast Saccharomyces

A diastatic strain of Saccharomyces cerevisiae producing the STA2-encoded extracellular glucoamylase (GA) in a pronounced glucose-repressible fashion was used as a parent for generating mutants with reduced GA activity under normal conditions of derepression. In addition to mutations in STA2, five other recessive mutations were identified which fell into four complementation groups designated haf1 through haf4. RNA blot analysis suggested that the haf mutations confer defects in STA2 transcription. The haf mutants were pleiotropically defective in utilization of alternative carbon sources and resembled the snf (sucrose non-fermenting) mutants identified previously as unable to derepress the expression of the SUC2 gene encoding invertase. We present evidence strongly suggesting that haf1 = snf2, haf3 = snf1 and haf4 = snf5. By phenotypic criteria, the postulated HAF2 gene (which is none of the SNF genes tested) appears to be similar to SNF2, SNF5 and SNF6, and is possibly a non-redundant extension of this group of functionally related SNF genes.