GROWTH-RELATED COORDINATE REGULATION OF THE EARLY N-GLYCOSYLATION GENES IN YEAST

The Saccharomyces cerevisiae ALG7, ALG1 and ALG2 genes, whose products function early in the dolichol pathway of protein N-glycosylation, ar e essential for cell viability, and perturbation in their expression c auses G(1)-specific cell cycle arrest. Here, we show that expression o f the ALG7, ALG1 and ALG2 genes is coordinately regulated at the G(0)/ G(1) transition point in the yeast life cycle. Carbon starvation, whic h induces cells to exit from the G(1) stage of the mitotic cycle into G(0), resulted in a time-dependent decrease in the levels of the early ALG genes' mRNAs. Accordingly, addition of glucose, which stimulates the G(0)-arrested cells to resume proliferation, resulted in a rapid i nduction of their mRNAs. Cycloheximide alone also induced the early AL G transcripts, albeit to a much lower extent than glucose. Simultaneou s addition of glucose and cycloheximide caused superinduction of these mRNAs, indicating that more than one control level was involved in th eir activation. Consistent with this, rapid degradation of ALG7, ALG1 and ALG2 mRNAs was completely abolished in the presence of cycloheximi de. These data suggest that in yeast, the early N-glycosylation genes are regulated ina manner similar to that of the early growth-response genes.