PRIMPOL competes with RAD51 to resolve G-quadruplex-induced replication stress via its interaction with RPA.

PRIMPOL (primase-polymerase) is a recently discovered DNA primase-polymerase involved in DNA damage tolerance and replication stress response in eukaryotic cells. However, the detailed mechanism of the PRIMPOL response to replication stress remains elusive. Here, we demonstrate that replication-related factors, including replication protein A (RPA), regulate the accumulation of PRIMPOL in subnuclear foci in response to replication stress induced by replication inhibitors. Moreover, PRIMPOL works at G-quadruplexes (G4s) in human cells to resolve the replication stress induced by G4s. The formation of PRIMPOL foci persists throughout the cell cycle. We further demonstrate that PRIMPOL competes with RAD51 to resolve G4-induced replication stress. In conclusion, our results provide novel insight into the mechanism of PRIMPOL in G4s to resolve replication stress and competition between PRIMPOL (repriming)- and RAD51 (fork reversal)-mediated pathways, which indicates a new strategy to improve the tumor response to DNA-damaging chemotherapy by targeting the PRIMPOL pathway.