ADP-ribosylation is a reversible posttranslational modification used to regulate protein function. ADP-ribosyltransferases (see ART1; MIM 601625) transfer ADP-ribose from NAD+ to the target protein, and ADP-ribosylhydrolases, such as ADPRHL1, reverse the reaction (Glowacki et al., 2002 [PubMed 12070318]).[supplied by OMIM, Mar 2008].