In budding yeast, reactive oxygen species induce both RAS-dependent and RAS-independent cell cycle-specific arrest

The role of mild oxidative stresses elicited by diethylmaleate (DEM)-induce d glutathione depletion in the progression of the yeast cell cycle has been investigated. We found that different wild-type strains are sensitive to o xidative stresses induced by similar DEM doses: approximate to 1 mM on YPD plates, 5-10 mM in shaken flasks, At lower doses, DEM caused a transient de crease in growth rate, largely because of a decreased G(1)-to-S transition. Treatment with higher DEM doses leads to complete growth arrest, with most cells found in the unbudded G(1) phase of the cell cycle. DEM treatment re sulted in transcriptional induction of stress-responsive Element (STRE)-con trolled genes and was relieved by treatment with the antioxidant N-acetyl c ysteine, Reciprocal shift experiments with cdc25 and cdc28 mutants showed t hat the major cell cycle arrest point was located in the Start area, at or near the CDC25-mediated step, before the step mediated by the CDC28 cyclin- dependent kinase, The DEM-induced G(1) arrest requires a properly regulated RAS pathway and can be bypassed by overexpressing the G(1)-specific cyclin CLN2. However, cells with either a deregulated RAS pathway or overexpressi ng CLN2 failed to grow and arrested as budded cells, indicating that a seco nd DEM-sensitive cell cycle step exists.