PARP1-mediated PARylation of SPRTN restrains its DNA-protein crosslink repair activity

SPRTN is a DNA-dependent metalloprotease that resolves DNA-protein crosslinks, but how its activity is restrained on chromatin remains unclear. Here we show that SPRTN is PARylated in a PARP1- and HPF1-dependent manner. Mass spectrometry datasets identify seven modified residues in the C-terminal region, and substituting them (SPRTN-PARless) strongly reduces PARylation. The Nudix homology domain is required for SPRTN to interact with PARP1 and for efficient PARylation. SPRTN-PARless accumulates faster and to higher levels at laser-induced DNA damage than wild-type SPRTN. PARylation reduces single-stranded DNA binding of both cell-derived and purified SPRTN, and PARG treatment reverses this effect for cell-derived protein. SPRTN-PARless shows increased autocleavage and accelerates clearance of camptotheci-induced TOP1 cleavage complexes. These findings suggest that PARylation acts as negative feedback on SPRTN after its PAR-dependent recruitment, restraining its DNA engagement and proteolytic activity.