WIP1 Promotes Homologous Recombination and Modulates Sensitivity to PARP Inhibitors

Abstract

Genotoxic stress triggers a combined action of DNA repair and cell cycle checkpoint pathways. Protein phosphatase 2C delta (referred to as WIP1) is involved in timely inactivation of DNA damage response by suppressing function of p53 and other targets at chromatin. Here we show that WIP1 promotes DNA repair through homologous recombination. Loss or inhibition of WIP1 delayed disappearance of the ionizing radiation-induced 53BP1 foci in S/G2 cells and promoted cell death. We identify breast cancer associated protein 1 (BRCA1) as interactor and substrate of WIP1 and demonstrate that WIP1 activity is needed for correct dynamics of BRCA1 recruitment to chromatin flanking the DNA lesion. In addition, WIP1 dephosphorylates 53BP1 at Threonine 543 that was previously implicated in mediating interaction with RIF1. Finally, we report that inhibition of WIP1 allowed accumulation of DNA damage in S/G2 cells and increased sensitivity of cancer cells to a poly-(ADP-ribose) polymerase inhibitor olaparib. We propose that inhibition of WIP1 may increase sensitivity of BRCA1-proficient cancer cells to olaparib.

Phosphorylation of PLK3 Is Controlled by Protein Phosphatase 6

“…Finally, we evaluated the dynamics of DNA damage response by quantification of γH2AX nuclear foci formation after exposure of cells to ionizing radiation. As expected, we observed an increase in the number of nuclear foci in control cells at an early time-point after exposure to IR followed by a decrease at a later time point corresponding to DNA repair [32]. However, formation and disappearance of the γH2AX nuclear foci was comparable in parental and RPE-PLK3-KO cells ( Figure 4H).…”

“…Images were analyzed using LAS AF Lite software (Leica, Wetzlar, Germany). Induction of DNA damage response was evaluated as described previously [32]. Briefly, cells were exposed to ionizing radiation (3 Gy) using X-RAD 225XL instrument (Precision; Cu filter 0.5 mm), fixed with 4% PFA, permeabilized with 0.5% Triton X1−00, and probed with antibody against γH2AX (Cell Signaling Technology).…”

Truncated PPM1D Prevents Apoptosis in the Murine Thymus and Promotes Ionizing Radiation-Induced Lymphoma

“…Sustained activation of p53 during G2 can lead to premature activation of Anaphase-promoting complex/cyclosome and its coactivator Cdh1 followed by degradation of cyclin B1 and induction of senescence [ 14 , 15 ]. The depletion of PPM1D leads to abnormally high activation of p53 during G2 and to defects in homologous recombination, both contributing to the loss of recovery competence and induction of senescence [ 10 , 16 , 17 ]. In addition, senescence can result from sustained activation of p53 during G1 through the expression of downstream genes including CDKN1A p21 [ 18 , 19 ].…”

Analysis of the association between KIN17 expression and the clinical features/prognosis of epithelial ovarian cancer, and the effects of KIN17 in SKOV3 cells

“…and the effects of KIN17 in SKOV3 cells in higher sensitivity to chemotherapy than in patients without BRCA1 gene mutations (11). It is estimated that ~50% of high-grade serous adenocarcinomas feature homologous recombination (3,12).…”

“…DNA DSBs are mainly repaired by homologous recombination signaling pathways ( 10 ). Previous research has demonstrated that homologous recombination defects are obvious in patients with ovarian cancer with BRCA1 gene mutations, resulting in higher sensitivity to chemotherapy than in patients without BRCA1 gene mutations ( 11 ). It is estimated that ~50% of high-grade serous adenocarcinomas feature homologous recombination ( 3 , 12 ).…”