RORα autoregulates its transcription via MLL4-associated enhancer remodeling in the liver

In hepatocytes, the retinoic acid receptor-related orphan receptor α (RORα) regulates the transcription of diverse genes encoding lipogenic enzymes, antioxidant enzymes, and mitochondrial factors via the regulation of the transcriptional activity of their promoters. The coordination of the expression of RORα by driving its transcription would provide better aspects for managing liver homeostasis.

The transcriptional expression of RORα was measured after treatment of RORα agonists on primary hepatocytes and liver. The histone status of Rora gene bodies was examined by analyzing ChIP-seq database. To elucidate molecular mechanism for RORα autoregulation, broad ChIP assays for promoters and enhancers with histone and RORα antibodies were performed.

We report that natural and synthetic RORα agonists, cholesterol sulfate and JC1-40, respectively, increased the transcriptional expression of RORα in primary hepatocytes. An analysis of histone status around the Rora gene body identified promoter and enhancer regions of RORα. We found that RORα indirectly increased histone acetylation of H3K9 at the promoter region and directly enhanced histone monomethylation of H3K4 by binding to enhancer regions. Interestingly, disturbance of mixed-lineage leukemia 4 (MLL4), a histone methyltransferase for enhancers, abolished the JC1-40-induced activation of RORα via a decrease in H3K4me1. Finally, we observed that the MLL4-mediated autoregulation of RORα also occurred in human liver cancer cell lines.

The ability of RORα to modulate its own transcription is crucial for liver homeostasis, and ligand-dependent autoregulation could amplify the therapeutic effects of RORα in fatty liver diseases.