An obligatory role of protein glycosylation in the life cycle of yeast cells.

In the presence of 2-4 micrograms tunicamycin/ml, yeast cells stop growth after the cell number has increased 1.5-1.7-fold. The cells are arrested in G1: the rate of DNA synthesis greatly decreases and the budding index drops from 0.6 to 0.1 RNA synthesis is inhibited concomitantly, whereas protein synthesis is little affected. It is postulated that for G1/S phase transition to occur one or more proteins have to be glycosylated.