Ps-b04-4: a novel hnf4a corepressor irf2bp2: its role in the gluconeogenic gene regulation via biochemically labile interaction

Hepatocyte nuclear factor 4α (HNF4α) has an essential role in controlling the expression of variety of genes involved in key metabolic pathways including gluconeogenesis in the liver. Though mechanistic and physiological significance of proliferator-activated receptor-gamma co-activator-1α (PGC-1α) for HNF4α-mediated transcriptional activation models for gluconeogenic genes is well characterized, transcriptional repression of HNF4α for those genes still remains to be examined. In this study, we applied novel proteomic techniques to evaluate the HNF4α interactome including biochemically labile binding proteins. From the experiment, we identified interferon regulatory factor 2 binding protein 2 (IRF2BP2) as a novel HNF4α corepressor, with which its interaction could not be detected by conventional immunoprecipitation. IRF2BP2 repressed transcriptional activity of HNF4α dependent on its E3 ubiquitin ligase activity. Deficiency of IRF2BP2 gene in HepG2 cells induced gluconeogenic genes comparable to the forskolin-treated wild type HepG2 cells. Together, these results suggest the role of IRF2BP2 as a novel class of nuclear receptor coregulator.