Hyperthermia and paraquat-induced G1 arrest in the yeast Saccharomyces cerevisiae is independent of the RAD9 gene.

Mutants of the RAD9 gene of Saccharomyces cerevisiae are defective in cell cycle checkpoint arrest in G1 and G2 after treatment with DNA-damaging agents. It is demonstrated that the pronounced G1 arrest observed in yeast after hyperthermia treatment or exposure to paraquat-generated superoxide radicals does not depend on a functional RAD9 gene. For both types of treatments, the mechanism of cell cycle arrest must be considered different from the activation of the DNA damage checkpoint response.