PARG regulates the proteasomal degradation of TARG1

ADP-ribosylation is a reversible modification of macromolecules critical for the regulation of genome stability, stress responses, and proteostasis. While the roles of ADPr transferases such as PARP1/2 and TNKS1/2 are well established, the functions and regulatory mechanisms of ADPr hydrolases are still poorly understood. Here, we identify a previously uncharacterized function of the poly(ADP-ribose) glycohydrolase PARG in regulating protein degradation. Using quantitative proteomics, we show that PARG inhibition depletes protein levels of the mono-ADPr hydrolase TARG1. We demonstrate that this TARG1 depletion is both PAR- and proteasome-dependent, and identify the E3 ubiquitin ligases HUWE1 and TRIP12 as mediators of this process. Our findings establish TARG1 as a substrate of PAR-dependent protein degradation and uncover a PARG-dependent mechanism controlling its stability. This work highlights a new dimension of interplay between the two ADP-ribosyl hydrolases, with implications for the refinement of PARG-targeted therapeutic strategies. Overall design: RNA-seq in biological triplicates of U2OS WT cells treated with either DMSO or PARGi