Regulation of gene expression by glucose in Saccharomyces cerevisiae: a role for ADA2 and ADA3/NGG1

When Saccharomyces cerevisiae cells are transferred from poor medium to fre sh medium containing glucose, they rapidly increase the transcription of a large group of genes as they resume rapid growth and accelerate progress th rough the cell cycle. Among those genes induced by glucose is CLN3, encodin g a G(1) cyclin that is thought to play a pivotal role in progression throu gh Start. Deletion of CLN3 delays the increase in proliferation normally ob served in response to glucose medium. ADA2 and ADA3/NGG1 are necessary for the rapid induction of CLN3 message levels in response to glucose. Loss of either ADA2 or ADA3/NGG1 also affects a large number of genes and inhibits the rapid global increase in transcription that occurs in response to gluco se. Surprisingly, these effects are transitory, and expression of CLN3 and total poly(A)(+) RNA appear normal when ADA2 or ADA3/NGG1 deletion mutants are examined in log-phase growth. These results indicate a role for ADA2 an d ADA3/NGG1 in allowing rapid transcriptional responses to environmental si gnals. Consistent with the role of the Ada proteins in positive regulation of CLN3, deletion of RPD3, encoding a histone deacetylase, prevented the do wn regulation of CLN3 mRNA in the absence of glucose.