Inhibition of poly(ADP-ribose)polymerase causes increased DNA strand breaks without decreasing strand rejoining in alkylated HeLa cells.

Treatment of alkylated HeLa cells with 3-aminobenzamide, an inhibitor of poly(ADP-ribose) polymerase, increased the number of DNA strand breaks but did not affect the rate of strand rejoining. This suggests that an increase in DNA incision, not a decrease in ligation, results from the inhibition of poly(ADP-ribose) polymerase in cells recovering from DNA damaged by alkylating agents.