Phosphatase 1 Nuclear Targeting Subunit Mediates Recruitment and Function of Poly (ADP-Ribose) Polymerase 1 in DNA Repair

Abstract

PARP, particularly PARP1, plays an essential role in the detection and repair of DNA single-strand breaks and double-strand breaks. PARP1 accumulates at DNA damage sites within seconds after DNA damage to catalyze the massive induction of substrate protein poly ADP-ribosylation (PARylation). However, the molecular mechanisms underlying the recruitment and activation of PARP1 in DNA repair are not fully understood. Here we show that phosphatase 1 nuclear targeting subunit 1 (PNUTS) is a robust binding partner of PARP1. Inhibition of PNUTS led to strong accumulation of endogenous DNA damage and sensitized the cellular response to a wide range of DNA-damaging agents, implicating PNUTS as an essential and multifaceted regulator of DNA repair. Recruitment of PNUTS to laser-induced DNA damage was similar to that of PARP1, and depletion or inhibition of PARP1 abrogated recruitment of PNUTS to sites of DNA damage. Conversely, PNUTS was required for efficient induction of substrate PARylation after DNA damage. PNUTS bound the BRCA1 C-terminal (BRCT) domain of PARP1 and was required for the recruitment of PARP1 to sites of DNA damage. Finally, depletion of PNUTS rendered cancer cells hypersensitive to PARP inhibition. Taken together, our study characterizes PNUTS as an essential partner of PARP1 in DNA repair and a potential drug target in cancer therapy. Significance: These findings reveal PNUTS as an essential functional partner of PARP1 in DNA repair and suggest its inhibition as a potential therapeutic strategy in conjunction with DNA-damaging agents or PARP inhibitors. See related commentary by Murai and Pommier, p. 2460

KRCC1: A potential therapeutic target in ovarian cancer

“…*, P value < .05 considered significant Repo-Man. 36,37,48 Expression of NIPP1, a nuclear targeting subunit that inhibits PP1 induced mitotic catastrophe, apoptosis, and reduced xenograft tumor growth. 38 Inhibition of Repo-Man, another chromatin targeting subunit of PP1CC decreased clonal growth and increased apoptosis, a phenotype recapitulated by KRCC1 silenced cells.…”

“…Several reports have implicated PP1 in the DNA damage checkpoint activation and in DNA repair. [36][37][38][39] Interestingly, silencing KRCC1 increased phosphorylation of H2AX at Ser139 (γH2AX), and CHK1 at Ser 345 while CHK2, ATM, and ATR were unchanged ( Figure 6E,). Similar results were obtained with tautomycin ( Figure 6F), a protein phosphatase inhibitor, with specificity towards PP1 at less than 10 nM 40 concentration.…”

Poly(ADP-Ribose)Polymerase (PARP) Inhibitors and Radiation Therapy

“…Over the past decade, inhibitors of PARP have emerged as a common monotherapy for certain subtypes of breast and ovarian cancers (Tangutoori et al, 2015). Moreover, preclinical data has demonstrated that PARP inhibition can increase radiosensitivity in cancer cells (Wang et al, 2019). The efficacy of combination therapies employing PARP inhibitors and external beam radiation has been demonstrated in the clinic, and several phase I clinical trials based on this approach have been completed at the time of writing (NCT00770471, NCT00649207, NCT01264432, NCT01477489, NCT01514201, NCT01657799), with results being available for some of them (Russo et al, 2009;Tangutoori et al, 2015;Dréan et al, 2016).…”

Upregulation of Phosphatase 1 Nuclear-Targeting Subunit (PNUTS) Is an Independent Predictor of Poor Prognosis in Prostate Cancer

“…Injection of the microRNA miR-34a, a natural downregulator of PNUTS, into glioblastoma xenograft tumors reduced telomere length [17] and targeting PNUTS with miR-383 induced cell cycle arrest in testicular embryonal carcinoma cells [18]. Most recently, it was shown that PNUTS is an essential partner of poly (ADP-ribose) polymerase 1 in DNA repair [19], making PNUTS a potential drug target in the therapy of DNA double-strand repairdeficient tumors.…”