Suppression of sodium arsenite-potentiated cytotoxicity of ultraviolet light by cycloheximide in Chinese hamster ovary cells.

Post-treatment with sodium arsenite synergistically increased the cytotoxicity of ultraviolet (UV) light. The potentiation of UV cytotoxicity by sodium arsenite was apparently suppressed by cycloheximide (CHM), a protein synthesis inhibitor. The protective effect of CHM against sodium arsenite-potentiated UV cytotoxicity was well correlated to its activity in inhibiting the synthesis of stress proteins, particularly a small polypeptide with a molecular weight of 8500 dalton. This small stress protein was demonstrated as ubiquitin by immunoprecipitation. Our results also showed that neither ubiquitin induction nor potentiation of UV cytotoxicity by post-treatment with sodium arsenite was observed in the stationary cells. Thus, we suggested that ubiquitin is possibly involved in the action of arsenite in potentiating UV-induced cell killing.