Oxidative stress can have a myriad of effects on many different cell types. The mechanisms by which these effects occur are not completely known. Chimeric proteins of the GAL4 DNA binding domain and Cdk4 or the GAL4 activation domain with p16, were expressed in the yeast two-hybrid system. Cells expressing these chimeric proteins were cultured with hydrogen peroxide and decreases in beta-galactosidase activity were observed when compared to cells incubated without hydrogen peroxide, When cells, which expressed the intact GAL4 binding protein, were cultured in the presence of hydrogen peroxide the opposite was observed. Incubation of cells with buthionine sulfoximine augmented these responses to hydrogen peroxide, These data suggest that one of the mechanisms by which oxidative stress acts is via the modulation of protein-protein interactions and demonstrate that the yeast two-hybrid system may be a model by which to study protein interactions due to oxidative stress.