High incidence of sister chromatid exchanges and chromatid interchanges in the conditions of lowered activity of poly(ADP-ribose)polymerase

The effect of lowering the activity of poly(ADP-ribose)polymerase on chromosome stability has been examined. Chinese hamster ovary cells, CHO-Kl grown in a nicotinamide-free medium exhibited an increased frequency of sister chromatid exchanges in a time-dependent manner. Furthermore, addition of m-aminobenzamide which is known to be a strong inhibitor of poly(ADP-ribose)polymerase caused a manyfold increase in the frequency of both sister chromatid exchanges and non-sister chromatid interchanges. These results suggest that appropriate levels of NAD and the activity of poly(ADP-ribose)polymerase are required for maintaining chromosome stability.