SUMOylation of PTEN promotes DNA end resection through directly dephosphorylating 53BP1 in homologous recombination repair

Homologous recombination (HR) repair for DNA double-strand breaks (DSBs) is critical for maintaining genome stability and cell survival. Nuclear PTEN plays a key role in HR repair, but the underlying mechanism remains largely elusive. We find that SUMOylated PTEN promotes HR repair but represses non-homologous end joining (NHEJ) repair by directly dephosphorylating 53BP1. During DNA damage responses (DDR), p14ARF was phosphorylated and then interacted efficiently with PTEN, thus promoting PTEN SUMOylation as an atypical SUMO E3 ligase. Interestingly, SUMOylated PTEN was subsequently recruited to the chromatin at DNA-break sites. This was because that SUMO1 conjugated to PTEN was recognized and bound by the SUMO-interacting motif (SIM) of BRCA1, which has been located to the core of 53BP1 foci on the chromatin during S/G2 stage. Further, these chromatin-loaded PTEN directly and specifically dephosphorylated pT543 of 53BP1, resulting in the dissociation of 53BP1-complex, which facilitated DNA end resection and ongoing HR repair. The SUMOylation-deficient PTENK254R mice also showed decreased DNA damage repair in vivo. Blocking PTEN SUMOylation pathway with either an SUMOylation inhibitor or a p14ARF(2-13) peptide sensitized tumor cells to chemotherapy. Our study therefore provides the new mechanistic understanding of PTEN in HR repair and clinical intervention of chemo-resistant tumors.