DEREGULATION OF THE FIRST N-GLYCOSYLATION GENE, ALG7, PERTURBS THE EXPRESSION OF G1 CYCLINS AND CELL-CYCLE ARREST IN SACCHAROMYCES-CEREVISIAE

The evolutionarily conserved ALG7 gene encodes the dolichol-P-dependen t N-acetylglucosamine-1-P transferase (GPT) and functions by initiatin g the dolichol pathway of protein N-glycosylation. In Saccharomyces ce revisiae, ALG7 has been shown to play a role in cell proliferation. Th e yeast alpha-factor-induced cell cycle arrest in G1 occurs, in part, by downregulation of CLN1 and CLN2. The function of ALG7 in G1 arrest was examined in alg7 mutants containing diminished GPT activity. In wi ld type, CLN1 and CLN2 mRNAs were rapidly downregulated, while in alg7 mutants, these transcripts were only transiently repressed before bec oming greatly augmented. Analyses of DNA contents and budding indices showed that alg7 mutants resumed cycling when wild type cells remained arrested. Thus, deregulation of ALG7 interferes with cell cycle arres t by preventing a sustained downregulation of CLN1 and CLN2 mRNAs. The se results provide a molecular insight into the role of ALG7, and prot ein N-glycosylation in general, in proliferation. (C) 1997 Academic Pr ess.