Identification of a novel stress-inducible glycoprotein in Saccharomyces cerevisiae. I. Preliminary characterization.
We have identified a novel stress-inducible protein in Saccharomyces cerevisiae by pulse-labeling with [35S]methionine and two-dimensional gel analysis. The protein was characterized biochemically to gain further insight into mechanisms regulating the stress response. It has a Mr = 118,000 and exists in two forms of pI = 4.2 (p118A) and pI = 4.3 (p118B). p118A and p118B are modified by N-glycosylation. Tunicamycin treatment revealed the presence of precursor proteins of Mr = 105,000, pI = 4.1 (p105A) and pI = 4.25 (p105B). The synthesis of p118A and p118B was almost completely shut off in cycling cells and was increased 11-fold following a mild heat shock. Both forms of p118 decayed in a biphasic manner under induced conditions. A tight correlation was observed in the kinetics of thermotolerance induction and p118A synthesis. Other forms of stress such as sulfur starvation which lead to arrest in the unbudded phase also resulted in enhanced synthesis of both p118A and p118B. However, in cell division cycle mutants blocked at various stages at the restrictive temperature, p118A and p118B had different synthetic patterns. Taken together, these data imply a role for induced p118 in proliferation arrest in the unbudded state.