A unified mechanism for PARP inhibitor-induced PARP1 chromatin retention at DNA damage sites in living cells
Petar-Bogomil Kanev,
Sylvia Varhoshkova,
Irina Georgieva,
Maria Lukarska,
Dilyana Kirova,
Georgi Danovski,
Stoyno Stoynov,
Radoslav Aleksandrov
Affiliations
Petar-Bogomil Kanev
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria
Sylvia Varhoshkova
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria
Irina Georgieva
Transmembrane Signaling Laboratory, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria
Maria Lukarska
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
Dilyana Kirova
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria
Georgi Danovski
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria
Stoyno Stoynov
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria; Corresponding author
Radoslav Aleksandrov
Laboratory of Genomic Stability, Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl.21, 1113 Sofia, Bulgaria; Corresponding author
Summary: Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) not only suppress PARP1 catalytic activity but also prolong its association to damaged chromatin. Here, through live-cell imaging, we quantify the alterations in PARP1 dynamics and activity elicited by seven PARPis over a wide range of concentrations to deliver a unified mechanism of PARPi-induced PARP1 chromatin retention. We find that gross PARP1 retention at DNA damage sites is jointly governed by catalytic inhibition and allosteric trapping, albeit in a strictly independent manner—catalytic inhibition causes multiple unproductive binding-dissociation cycles of PARP1, while allosteric trapping prolongs the lesion-bound state of PARP1 to greatly increase overall retention. Importantly, stronger PARP1 retention produces greater temporal shifts in downstream DNA repair events and superior cytotoxicity, highlighting PARP1 retention, a complex but precisely quantifiable characteristic of PARPis, as a valuable biomarker for PARPi efficacy. Our approach can be promptly repurposed for interrogating the properties of DNA-repair-targeting compounds beyond PARPis.
