Abstract 4092: Alteration of caspase-mediated events following DNA damage due to the absence of poly(ADP-ribose) glycohydrolase

Abstract

Abstract The synthesis of poly(ADP-ribose) (PAR) is an immediate cellular response to DNA damaging stresses. We reported previously that the absence of PAR glycohydrolase (PARG) led to increased cell death following DNA-damaging treatments. OBJECTIVE: To investigate the possible mechanism underlying the ability of PARG inhibition to produce cell hypersensitivity of DNA-damaging stresses. METHODS: Utilizing PARG null trophoblast stem (TS) cells, DNA damage following treatment with N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) or UV radiation were examined by immunocytochemistry. Cell viability was measured by DAPI staining and caspase 3/7 activity was measured by activity assay and the immunoblotting detection of procaspase-3 and PARP-1 cleavage. RESULTS: Increased amounts of DNA alkylation and UV-induced DNA damage were observed in PARG null TS cells. In addition, elevated amounts of cell death were detected following those treatments. However, both procaspase-3 and PARP-1 cleavage were detected at decreased levels and in a delayed fashion after UV treatment in PARG null TS cells. Caspase-3/7 activity assay confirmed the decreased activation of caspase-3/7 in PARG null-TS cells. Furthermore, PARG null-TS cells exhibited less caspase-3/7 activity after UV radiation than wild type TS cells. CONCLUSION: The results show that the functionality of caspase-3 following DNA damage is decreased and delayed due to the absence of PARG. This suggests that PAR or PARG itself may play a role in modulating caspase-mediated apoptosis after UV-induced DNA damage and cell death. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4092. doi:10.1158/1538-7445.AM2011-4092