PARP1 recruits SPRTN to DNA-protein crosslinks through a conserved poly-ADP-ribose binding domain.

Abstract

DNA-protein crosslinks (DPCs) are toxic DNA lesions formed by the covalent attachment of proteins to DNA. Failure to resolve DPCs leads to genomic instability, premature aging, and cancer predisposition. Although multiple proteases and the 26S proteasome degrade DPCs, how these lesions are detected and marked for proteolysis remains unclear. Here, we show that poly-(ADP-ribose) polymerases (PARP1/2) sense DPCs and modify them with poly(ADP-ribose) (PAR) to promote repair via a SPRTN-Tdp1 axis. We discovered a Nudix homology domain (NHD) in SPRTN that mediates direct non-covalent PAR binding and is important for DPC repair. Loss of PARP1/2 activity or mutation of the SPRTN NHD leads to sustained DPCs. Single-molecule analysis revealed that SPRTN does not bind efficiently to the DPC, however after the addition of PARP1 in the presence of NAD+, SPRTN binding to the DPC was significantly increased. Our findings establish PARP1/2 enzymes as immediate DPC sensors, reveal PARylation as a signal marking DPCs for SPRTN-dependent degradation, and identify SPRTN as the first PARP-directed protease.