Combinatorial regulation of hepatic cytoplasmic signaling and nuclear transcriptional events by the OGT/REV-ERB? complex.
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ABSTRACT: The nuclear receptor REV-ERB? integrates the circadian clock with hepatic glucose and lipid metabolism by nucleating transcriptional comodulators at genomic regulatory regions. An interactomic approach identified O-GlcNAc transferase (OGT) as a REV-ERB?-interacting protein. By shielding cytoplasmic OGT from proteasomal degradation and favoring OGT activity in the nucleus, REV-ERB? cyclically increased O-GlcNAcylation of multiple cytoplasmic and nuclear proteins as a function of its rhythmically regulated expression, while REV-ERB? ligands mostly affected cytoplasmic OGT activity. We illustrate this finding by showing that REV-ERB? controls OGT-dependent activities of the cytoplasmic protein kinase AKT, an essential relay in insulin signaling, and of ten-of-eleven translocation (TET) enzymes in the nucleus. AKT phosphorylation was inversely correlated to REV-ERB? expression. REV-ERB? enhanced TET activity and DNA hydroxymethylated cytosine (5hmC) levels in the vicinity of REV-ERB? genomic binding sites. As an example, we show that the REV-ERB?/OGT complex modulates SREBP-1c gene expression throughout the fasting/feeding periods by first repressing AKT phosphorylation and by epigenomically priming the Srebf1 promoter for a further rapid response to insulin. Conclusion: REV-ERB? regulates cytoplasmic and nuclear OGT-controlled processes that integrate at the hepatic SREBF1 locus to control basal and insulin-induced expression of the temporally and nutritionally regulated lipogenic SREBP-1c transcript.
SUBMITTER: Berthier A
PROVIDER: S-EPMC6255172 | biostudies-literature | 2018 Nov
REPOSITORIES: biostudies-literature
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