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

초록

Aims: In hepatocytes, the retinoic acid receptor-related orphan receptor alpha (ROR alpha) 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 ROR alpha by driving its transcription would provide better aspects for managing liver homeostasis. Main methods: The transcriptional expression of ROR alpha was measured after treatment of ROR alpha agonists on primary hepatocytes and liver. The histone status of Ror alpha gene bodies was examined by analyzing ChIP-seq database. To elucidate molecular mechanism for ROR alpha autoregulation, broad ChIP assays for promoters and enhancers with histone and ROR alpha antibodies were performed. Key findings: We report that natural and synthetic ROR alpha agonists, cholesterol sulfate and JC1-40, respectively, increased the transcriptional expression of ROR alpha in primary hepatocytes. An analysis of histone status around the Ror alpha gene body identified promoter and enhancer regions of ROR alpha. We found that ROR alpha 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 ROR alpha via a decrease in H3K4mel. Finally, we observed that the MLL4-mediated autoregulation of ROR alpha also occurred in human liver cancer cell lines. Significance: The ability of ROR alpha to modulate its own transcription is crucial for liver homeostasis, and ligand-dependent autoregulation could amplify the therapeutic effects of ROR alpha in fatty liver diseases.

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