NF-kappaB-induced activation of proinflammatory genes can be completely repressed by the glucocorticoid receptor upon hormone binding. However, critical cofactors and mechanism that transmit the glucocorticoid signal into the NF-kappaB pathway remain elusive. We recently defined O-GIcNAc transferase (OGT) as an atypical mediator in gene repression. Hence, our first specific aim is to explore the role of this enzyme as a candidate corepressor for the glucocorticoid receptor in antiinflammatory responses. We will test a physical interaction between OGT and the glucocorticoid receptor by biochemical approaches and will examine their functional interaction by cell-based gene reporter assays. Using RNA interference, we will assess a possible role of OGT in regulating endogenous proinflammatory genes. Unlike OGT, little is known about the impact of the opposing enzyme O-Incase (OGN) on transcription. Hence, our second specific aim is to discern how these two reciprocal enzymes contribute to the activation or inhibition of the proinflammatory genetic network. Using a chromatin immunoprecipitation assay, we will study the dynamics of OGT and OGN at the promoters of either active or repressive proinflammatory genes. Moreover, we will seek to identify upstream regulators and downstream targets of these two enzymes in the transcriptional apparatus through biochemical approaches. This study is designed to delineate a precise mechanism by which O-GIcNAc regulates transcription. As glucocorticoids are currently used to treat inflammation and cancer, understanding their action via O-GIcNAc offers a new approach to treatment and drug designs.
| Li, Min-Dian; Ruan, Hai-Bin; Singh, Jay P et al. (2012) O-GlcNAc transferase is involved in glucocorticoid receptor-mediated transrepression. J Biol Chem 287:12904-12 |
