PARP-1 Controls the Adipogenic Transcriptional Program by PARylating C/EBPβ and Modulating Its Transcriptional Activity

Poly(ADP-ribosyl)ation (PARylation) is a regulatory post-translational modification of proteins mediated by PARP family members, such as PARP-1. Although PARP-1 and PARylation have been widely studied, very few examples of definitive biological roles for site-specific PARylation of proteins exist in the literature. Here we show that C/EBPβ, a key pro-adipogenic transcription factor, is PARylated by PARP-1 at Glu135, as well as two adjacent amino acids (K133 and E139). PARylation at these sites inhibits C/EBPβ’s DNA binding and transcriptional activities, and attenuates adipogenesis in various cell-based models of adipogenesis. Interestingly, PARP-1 catalytic activity drops precipitously during the first 48 hours of hormone-induced differentiation, corresponding to a release of C/EBPβ from PARylation-mediated inhibition. This allows the binding of C/EBPβ to the promoters of pro-adipogenic target genes (e.g., Cebpa, Pparg2), their subsequent expression, and continued differentiation. In this regard, depletion of PARP-1 or chemical inhibition of its catalytic activity enhances early adipogenic events. Collectively, our results provide a clear example of how site-specific PARylation of a key transcription factor can affect its molecular and biochemical functions, as well as the biological outcomes that it controls. ChIP-seq (C/EBP beta) were perfomed in 3T3-L1 cells expressing doxycycline inducible HA tagged C/EBP beta LAP wildtype and PARylation site mutant, with or without doxycycline and PARP inhibitor treatment.