Effect of 3-aminobenzamide on the cell cycle in x-irradiated Chinese hamster cells replicating in medium containing 5-bromodeoxyuridine

A specific inhibitor of poly(ADP-ribose)polymerase- 3 -aminobenzamide (6 mM) has been shown to: 1) reduce survival of non-irradiated CHO-Kl cells, cultivated in medium containing 5-bromodeoxyuridine (10 mkM, BDU-cells), and increase their radiosensitivity; 2) induce G2-delay in BDU-cells while progressing through the cell cycle as analysed by the DNA flow cytometry; 3) increase to a great degree G2-delay in X-irradiated BDU-cells. 3-Aminobenzamide is primarily effective when it is present during the first or two first cell cycles after the initial addition of BDU. The above data confirm the involvement, presumably an indirect one, of ADP-ribosylation in the DNA repair through affecting the chromatin structure