TRANSCRIPT ACCUMULATION OF THE GGP1-GENE, ENCODING A YEAST GPI-ANCHORED GLYCOPROTEIN, IS INHIBITED DURING ARREST IN THE G(1)-PHASE AND DURING SPORULATION

The GGP1 (GAS1) gene encodes an exocellular 115-kDa glycoprotein (gp115) of the yeast Saccharomyces cerevisiae. We have monitored the changes in GGP1 mRNA levels under different conditions of G1 arrest. Transcript levels rapidly decrease during transition from exponential growth to stationary phase. They also decrease in the ts cdc25 and cdc28 START mutants when brought to the restrictive temperature. In cells arrested in G1 by alphaF treatment, the GPP1 mRNA level undergoes a threefold reduction. During release from the G1 block the mRNA level rapidly increases with a maximum at the onset of budding. During sporulation GGP1 mRNA level steadily decreases. These results indicate that the accumulation of the GGP1 transcript is inhibited during arrest in the G1 phase and during entry into the differentiative pathway of meiosis and sporulation. The induction of expression upon entry into the mitotic cycle suggests that GGP1 could be one of the genes whose transcription is activated at START.