GNL3 SUMOylation is essential for DNA double-strand break repair by homologous recombination

ABSTRACT: DNA double-strand break (DSB) repair via homologous recombination (HR) is critical for maintaining genomic integrity and requires proper DNA end resection to generate ssDNA overhangs. Yet, how this critical step is regulated in cells remains to be understood. Here, we report that GNL3, a nucleolar GTP-binding protein, plays a critical role in HR repair via regulating DNA end resection dependently on its SUMOylation. Ectopic expression of wild-type, but not the SUMO-defective K196R mutant, GNL3 completely abolished DNA damage response induced by knockdown of endogenous GNL3. GNL3 interacts with the BLM-DNA2 helicase-nuclease complex and is critical for DNA end resection and subsequent RPA and RAD51 loading. The GNL3-BLM interaction requires SUMOylation and SUMO-interacting motifs (SIMs) of both proteins. We further showed that USP36, a nucleolar deubiquitinating enzyme, acts as a novel SUMO ligase for GNL3, whereas SUMOylated GNL3 can be deSUMOylated by the SUMO protease SENP3. Interestingly, several breast cancer-derived variants of GNL3 that interfere with its SUMOylation of SIM failed to interact with the BLM-DNA2 complex. Knockdown of GNL3 sensitizes breast cancer cells to the treatment with etoposide or Olaparib. Together, our results reveal that GNL3 SUMOylation is critical for HR repair and targeting GNL3 SUMOylation may induce HR deficiency and sensitize breast cancers to DNA damage-inducing agents.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Phillip Wilmarth  

LAB HEAD: Mu-Shui Dai

PROVIDER: PXD068465 | Pride | 2026-06-16

REPOSITORIES: Pride