SUN-650 Molecular Determinants of PARP1 Catalytic Activity and Substrate Selection in Adipocytes

Abstract Disclosure: W. Song: None. T.S. Nandu: None. W.L. Kraus: SigmaMillipore. Adipogenesis is a complex and tightly regulated process that plays a vital role in multiple aspects of human health. We have previously shown that ADP-ribosylation (ADPRylation), a posttranslational modification of proteins, regulates multiple steps during the differentiation of preadipocytes to adipocytes. Enzymes of the PARP family catalyze the covalent attachment of ADP-ribose units from NAD+ on specific amino acid acceptors in proteins. PARP1-mediated, site-specific ADP-ribosylation on substrate proteins controls multiple components of the proadipogenic gene regulatory machinery, including histone H2B and the transcription factor C/EBPβ. Our recent studies have revealed that small nucleolar RNAs (snoRNAs) can activate PARP1 catalytic activity in a DNA-independent manner. Moreover, the depletion of PARP1-interacting snoRNAs enhance the expression of adipocyte marker genes upon differentiation. We hypothesize that snoRNA-activated PARP1 ADPRylates its substrate proteins in a site-specific manner to control adipogenesis. Using an NAD+ analog-sensitive PARP1 approach with a “clickable” NAD+ analog and copper-catalyzed azide-alkyne cycloaddition (“click chemistry”) developed in our lab, we identified substrate proteins ADPRylated by snoRNA-activated PARP1, including several transcription factors. These results suggest that snoRNA-activated PARP1 can regulate gene expression by ADPRylating these transcription factors. We are currently determining how snoRNA-activated PARP1 selects its substrates for modification. Ongoing investigations are exploring (1) the molecular and biochemical mechanisms of the snoRNA-mediated PARP1 catalytic activity and (2) the regulatory roles of the snoRNA-activated PARP1 and its substrate proteins during adipogenesis. Collectively, these studies will explore snoRNA-mediated PARP1 activation and site-specific ADPRylation of key substrate proteins, which will provide insights into the role of PARP1 in the regulation of adipogenesis. Presentation: Sunday, July 13, 2025