Inhibition of protein synthesis antagonizes induction of sister-chromatid exchanges by exogenous agents.

Cycloheximide (CH) and puromycin (PM)strongly antagonize induction of sister-chromatid exchanges (SCEs) by exogenous agents regardless of the mechanism for initiating damage. 5-Bromodeoxyuridine (BUdR) substitution was used to monitor SCEs, but the background level of BUdR-induced SCEs was unaffected by the presence of protein inhibitors. Antagonism between DNA-damaging agents and protein inhibitors was strongest in euchromatic regions. Possible relationships between SCE formation and the mechanism of antagonism by protein inhibitors are discussed.