INCREASED SENSITIVITY TO DNA-ALKYLATING AGENTS IN CHO MUTANTS WITH DECREASED POLY(ADP-RIBOSE) POLYMERASE-ACTIVITY

Using a replica-plating procedure and a P-32-NAD(+) permeable cell-scr eening assay, we have isolated a CHO mutant, PADR-9, which displays ap proximately 17% of the wild-type level of poly(ADP-ribose) polymerase activity. Biochemical analysis of the mutant using activity, Western, and Northern blot techniques indicate that relative to its parent cell , the mutant's enzyme activity, antibody recognition, and mRNA levels have been reduced to approximately the same extent. These results are consistent with a mutation in the PADR-9 cell which has resulted in a reduction in enzyme synthesis due to reduced mRNA synthesis and/or sta bility. Relative to wild-type CHO cells, the PADR-9 mutant has increas ed sensitivity to killing by DNA-alkylating agents but has normal gamm a-ray sensitivity. Correlation between a decrease in poly(ADP-ribose) polymerase activity and an increased sensitivity to DNA-alkylating age nts suggests that poly(ADP-ribose) synthesis may be important in the r epair and/or induction of DNA damage produced by these agents.