Induction by adozelesin and hydroxyurea of origin recognition complex-dependent DNA damage and DNA replication checkpoints in Saccharomyces cerevisiae

DNA damaging agents induce a conserved intra-S-phase checkpoint that inhibi ts DNA replication in eukaryotic cells. To better understand this checkpoin t and its role in determining the efficacy of antitumor drugs that damage D NA, we examined the effects of adozelesin, a DNA-alkylating antitumor agent that has a profound inhibitory effect on initiation of DNA replication in mammals, on the replication of Saccharomyces cerevisiae chromosomes. Adozel esin inhibited initiation of S, cerevisiae DNA replication by inducing an i ntra-S-phase DNA damage checkpoint. This inhibitory effect was abrogated in orc2-1 cells containing a temperature-sensitive mutation in a component of the origin recognition complex (ORC) that also causes a defect in initiati on. The orc2-1 mutation also caused a defect in a checkpoint that regulates the activation of origins in late S phase in cells treated with hydroxyure a, Defects in both initiation and checkpoint regulation in the orc2-1 strai n were suppressed by deletion of a gene encoding a putative acetyltransfera se, SAS2, Adozelesin also induced a cellular response that requires a funct ion of ORC in G(1). A similar G(1)-specific response in mammals may contrib ute to the cytotoxic and antitumor properties of this and other DNA-damagin g drugs.