EXPRESSION OF THE FIRST N-GLYCOSYLATION GENE IN THE DOLICHOL PATHWAY,ALG7, IS REGULATED AT 2 MAJOR CONTROL POINTS IN THE G1 PHASE OF THE SACCHAROMYCES-CEREVISIAE CELL-CYCLE

The Saccharomyces cerevisiae ALG7 gene, which functions by initiating the dolichol pathway of protein N-glycosylation, displays properties o f an early growth-response gene. To initiate studies of the involvemen t of ALG7 in cellular proliferation, we have now more precisely analyz ed ALG7 expression in the G1 phase of cell cycle. We show that the rap id rate of ALG7 mRNA accumulation following growth stimulation was att enuated soon thereafter and that ALG7 growth induction occurred irresp ective of alpha-factor. ALG7 growth induction was observed in mutants conditionally defective for reentry into the cell cycle from the stati onary phase, indicating that the induction occurred prior to the perfo rmance of START. In addition, the steady-state levels of ALG7 mRNAs de clined four fold in response to START-I cell division arrest brought a bout by alpha-factor treatment later in G1. Importantly, deregulated e xpression of ALG7 resulted in an aberrant alpha-factor response. Our d ata not only indicate that ALG7 expression is regulated at two critica l control points in G1 that determine the proliferative potential of c ells, but also provide a link between ALG7 and START. (C) 1995 Academi c Press, Inc.