The ZGRF1 Helicase Promotes Recombinational Repair of Replication-Blocking DNA Damage in Human Cells
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Replication-blocking DNA lesions are particularly toxic to proliferating cells because they can lead to chromosome missegregation if not repaired prior to mitosis. In this study, we report thatZGRF1null cellsaccumulate chromosome aberrations following replication perturbation and show sensitivity to two potentreplication-blocking anticancer drugs: mitomycin C and camptothecin. Moreover,ZGRF1null cells are defective in catalyzing DNA damage-induced sister chromatid exchange despite accumulating excessive FANCD2,RAD51, andg-H2AX foci upon induction of interstr and DNA crosslinks. Consistent with a direct role in promoting recombinational DNA repair, we show that ZGRF1 is a 50-to-30helicase that catalyzes D-loop dissociation and Holliday junction branch migration. Moreover, ZGRF1 physically interacts with RAD51 and stimulates strand exchange catalyzed by RAD51-RAD54. On the basis of these data, we propose that ZGRF1 promotes repair of replication-blocking DNA lesions through stimulation of homologous recombination.