GENETIC-ANALYSIS OF GLUCOSE REGULATION IN SACCHAROMYCES-CEREVISIAE - CONTROL OF TRANSCRIPTION VERSUS MESSENGER-RNA TURNOVER

A major determinant of the steady-state level of the mRNA encoding the iron protein (Ip) subunit of succinate dehydrogenase of yeast is its rate of turnover, This mRNA is significantly more stable in glycerol t han in glucose media, Many other genes, for example SUC2, that are rep ressed in the presence of glucose are believed to be controlled at the level of transcription, The present study elucidates differences in t he regulatory mechanisms by which glucose controls the transcription a nd turnover of the SUC2 and Ip mRNAs. The signaling pathway for glucos e repression at the transcriptional level has been associated with a n umber of gene products linking glucose uptake with nuclear events, We have investigated whether the same genes are involved in the control o f Ip mRNA stability, Phosphorylation of glucose or fructose is critica l in triggering the transcript's degradation, but any hexokinase will do, Of the other known genes examined, most, with the exception of REG 1, are not involved in determining the differential stability of the I p transcript, Finally, our results indicate that differential stabilit y on different carbon sources also plays a role in determining the ste ady-state level of the SUC2 mRNA. Thus, glucose repression includes bo th transcriptional and post-transcriptional mechanisms.