ABSTRACT. Blocking aldehyde dehydrogenase with the drug disulfiram leads to an accumulation of intracellular acetaldehyde, which negatively affects the viability of the yeast Saccharomyces cerevisiae. Mutants of the yeast gene PSO2, which encodes a protein specific for repair of DNA interstrand cross-links, showed higher sensitivity to disulfiram compared to the wild type. This leads us to suggest that accumulated acetaldehyde induces DNA lesions, including highly deleterious interstrand crosslinks. Acetaldehyde induced the expression of a PSO2-lacZ reporter construct that is specifically inducible by bi-or poly-functional mutagens, e.g., nitrogen mustard and photo-activated psoralens. Chronic exposure of yeast cells to disulfiram and acute exposure to acetaldehyde induced forward mutagenesis in the yeast CAN1 gene. Disulfiram-induced mutability of a pso2∆ mutant was significantly increased over that of the isogenic wild type; however, this was not found for acetaldehydeinduced mutagenesis. Spontaneous mutability at the CAN1 locus was elevated in pso2∆, suggesting that growth of glucose-repressed yeast 49 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 9 (1): 48-57 (2010) Disulfiram induces DNA damage in yeast produces DNA lesions that, in the absence of Pso2p-mediated crosslink repair, are partially removed by an error-prone DNA repair mechanism. The use of disulfiram in the control of human alcohol abuse increases cellular acetaldehyde pools, which, based on our observations, enhances the risk of mutagenesis and of other genetic damage.