Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Chao Wang
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Min Huang
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Xiaoguang Liu
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Xu Feng
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Mengfan Tang
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Siting Li
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Qinglei Hang
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Hongqi Teng
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States
Xi Shen
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, United States; Institute for Personalized Cancer Therapy, The University of Texas MD Anderson Cancer Center, Houston, United States
Poly(ADP-ribose)ylation or PARylation by PAR polymerase 1 (PARP1) and dePARylation by poly(ADP-ribose) glycohydrolase (PARG) are equally important for the dynamic regulation of DNA damage response. PARG, the most active dePARylation enzyme, is recruited to sites of DNA damage via pADPr-dependent and PCNA-dependent mechanisms. Targeting dePARylation is considered an alternative strategy to overcome PARP inhibitor resistance. However, precisely how dePARylation functions in normal unperturbed cells remains elusive. To address this challenge, we conducted multiple CRISPR screens and revealed that dePARylation of S phase pADPr by PARG is essential for cell viability. Loss of dePARylation activity initially induced S-phase-specific pADPr signaling, which resulted from unligated Okazaki fragments and eventually led to uncontrolled pADPr accumulation and PARP1/2-dependent cytotoxicity. Moreover, we demonstrated that proteins involved in Okazaki fragment ligation and/or base excision repair regulate pADPr signaling and cell death induced by PARG inhibition. In addition, we determined that PARG expression is critical for cellular sensitivity to PARG inhibition. Additionally, we revealed that PARG is essential for cell survival by suppressing pADPr. Collectively, our data not only identify an essential role for PARG in normal proliferating cells but also provide a potential biomarker for the further development of PARG inhibitors in cancer therapy.
