A temperature-sensitive N-glycosylation mutant of S. cerevisiae that behaves like a cell-cycle mutant

The temperature-sensitive S. cerevisiae mutant alg1-1, defective in the N-glycosylation of proteins, shows a first cycle arrest at the non-permissive temperature of 36 degrees C. The cell number increases by 50% and the absorbance approximately doubles. The budding index of 0.4 at 26 degrees C drops to 0.15 and DNA synthesis quickly comes to a halt at 36 degrees C. When the temperature is lowered again, budding and DNA synthesis start after a lag of 2-3 h; alpha-factor prevents both these processes in cells of mating type a. In addition, cells arrested at 26 degrees C in G1 with alpha-factor also do not start budding at the non-permissive temperature after removal of alpha-factor. The results support recent findings obtained with tunicamycin and suggest that at least one glycoprotein is required for G1-S phase transition in yeast.