期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2012
卷号：109
期号：17
页码：6590-6595
DOI：10.1073/pnas.1118078109
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Poly(ADP-ribose) polymerase (PARP) inhibitors can generate synthetic lethality in cancer cells defective in homologous recombination. However, the mechanism(s) by which they affect DNA repair has not been established. Here we directly determined the effects of PARP inhibition and PARP1 depletion on the repair of ionizing radiation-induced single- and double-strand breaks (SSBs and DSBs) in human lymphoid cell lines. To do this, we developed an in vivo repair assay based on large endogenous Epstein-Barr virus (EBV) circular episomes. The EBV break assay provides the opportunity to assess quantitatively and simultaneously the induction and repair of SSBs and DSBs in human cells. Repair was efficient in G1 and G2 cells and was not dependent on functional p53. shRNA-mediated knockdown of PARP1 demonstrated that the PARP1 protein was not essential for SSB repair. Among 10 widely used PARP inhibitors, none affected DSB repair, although an inhibitor of DNA-dependent protein kinase was highly effective at reducing DSB repair. Only Olaparib and Iniparib, which are in clinical cancer therapy trials, as well as 4-AN inhibited SSB repair. However, a decrease in PARP1 expression reversed the ability of Iniparib to reduce SSB repair. Because Iniparib disrupts PARP1-DNA binding, the mechanism of inhibition does not appear to involve trapping PARP at SSBs.
