The trans cell cycle effects of PARP inhibitors underlie their selectivity toward BRCA1/2-deficient cells
Open Access
- 12 August 2021
- journal article
- research article
- Published by Cold Spring Harbor Laboratory in Genes & Development
- Vol. 35 (17-18), 1271-1289
- https://doi.org/10.1101/gad.348479.121
Abstract
PARP inhibitor (PARPi) is widely used to treat BRCA1/2-deficient tumors, but why PARPi is more effective than other DNA-damaging drugs is unclear. Here, we show that PARPi generates DNA double-strand breaks (DSBs) predominantly in a trans cell cycle manner. During the first S phase after PARPi exposure, PARPi induces single-stranded DNA (ssDNA) gaps behind DNA replication forks. By trapping PARP on DNA, PARPi prevents the completion of gap repair until the next S phase, leading to collisions of replication forks with ssDNA gaps and a surge of DSBs. In the second S phase, BRCA1/2-deficient cells are unable to suppress origin firing through ATR, resulting in continuous DNA synthesis and more DSBs. Furthermore, BRCA1/2-deficient cells cannot recruit RAD51 to repair collapsed forks. Thus, PARPi induces DSBs progressively through trans cell cycle ssDNA gaps, and BRCA1/2-deficient cells fail to slow down and repair DSBs over multiple cell cycles, explaining the unique efficacy of PARPi in BRCA1/2-deficient cells.Keywords
Funding Information
- Canadian Institutes of Health Research
- Fonds de recherche du Québec-Santé
- National Institutes of Health (CA240243, CA197779, CA218856)
- Gray Foundation
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