RESUMO
The clinical success of PARP1/2 inhibitors (PARPi) prompts the expansion of their applicability beyond homologous recombination deficiency. Here, we demonstrate that the loss of the accessory subunits of DNA polymerase epsilon, POLE3 and POLE4, sensitizes cells to PARPi. We show that the sensitivity of POLE4 knockouts is not due to compromised response to DNA damage or homologous recombination deficiency. Instead, POLE4 loss affects replication speed leading to the accumulation of single-stranded DNA gaps behind replication forks upon PARPi treatment, due to impaired post-replicative repair. POLE4 knockouts elicit elevated replication stress signaling involving ATR and DNA-PK. We find POLE4 to act parallel to BRCA1 in inducing sensitivity to PARPi and counteracts acquired resistance associated with restoration of homologous recombination. Altogether, our findings establish POLE4 as a promising target to improve PARPi driven therapies and hamper acquired PARPi resistance.
Assuntos
Proteína BRCA1 , DNA Polimerase II , Replicação do DNA , Inibidores de Poli(ADP-Ribose) Polimerases , Inibidores de Poli(ADP-Ribose) Polimerases/farmacologia , Humanos , Proteína BRCA1/genética , Proteína BRCA1/metabolismo , DNA Polimerase II/metabolismo , DNA Polimerase II/genética , Replicação do DNA/efeitos dos fármacos , Dano ao DNA , Linhagem Celular Tumoral , Recombinação Homóloga/genética , Recombinação Homóloga/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genéticaRESUMO
Poly(ADP-ribose) polymerase (PARP) inhibitors are used in the treatment of BRCA-deficient cancers, with treatments currently extending toward other homologous recombination defective tumors. In a genome-wide CRISPR knockout screen with olaparib, we identify ALC1 (Amplified in Liver Cancer 1)-a cancer-relevant poly(ADP-ribose)-regulated chromatin remodeling enzyme-as a key modulator of sensitivity to PARP inhibitor. We found that ALC1 can remove inactive PARP1 indirectly through binding to PARylated chromatin. Consequently, ALC1 deficiency enhances trapping of inhibited PARP1, which then impairs the binding of both nonhomologous end-joining and homologous recombination repair factors to DNA lesions. We also establish that ALC1 overexpression, a common feature in multiple tumor types, reduces the sensitivity of BRCA-deficient cells to PARP inhibitors. Together, we conclude that ALC1-dependent PARP1 mobilization is a key step underlying PARP inhibitor resistance.