A desthiobiotin labelled NAD analogue to uncover Poly(ADP-ribose) polymerase 1 protein targets.

ADP-ribosylation is a post-translational modification catalyzed by the enzyme family of polyadenosine diphosphate (ADP)-ribose) polymerases (PARPs). This enzymatic process involves the transfer of single or multiple ADP-ribose molecules onto proteins, utilizing nicotinamide adenine dinucleotide (NAD ) as a substrate. It, thus, plays a pivotal role in regulating various biological processes. Unveiling PARP-selective protein targets is crucial for a better understanding of their biological functions. Nonetheless, this task proves challenging due to overlapping targets shared among PARP family members. Therefore, we applied the "bump-and-hole" strategy to modify the nicotinamide binding site of PARP1 by introducing a hydrophobic pocket ("hole"). This PARP1-mutant binds an orthogonal NAD (Et-DTB-NAD ) containing an ethyl group ("bump") at the nicotinamide moiety. Furthermore, we added a desthiobiotin (DTB) tag directly to the adenosine moiety, enabling affinity enrichment of ADP-ribosylated proteins. Employing this approach, we successfully identified protein targets modified by PARP1 in cell lysate. This strategy expands the arsenal of chemically modified NAD analogs available for studying ADP-ribosylation, providing a powerful tool to study these critical post-translational modifications.