Rev-erb beta regulates the Srebp-1c promoter and mRNA expression in skeletal muscle cells

The nuclear hormone receptor, Rev-erb beta operates as a transcriptional silencer. We previously demonstrated that exogenous expression of Rev-erbβΔE in skeletal muscle cells increased Srebp-1c mRNA expression. We validated these in vitro observations by injection of an expression vector driving Rev-erbβΔE expression into mouse tibialis muscle that resulted in increased Srebp-1c mRNA expression. Paradoxically, Rev-erbβ siRNA expression in skeletal muscle cells repressed Srebp-1c expression, and indicated that Rev-erbβ expression was necessary for Srebp-1c expression. ChIP analysis demonstrated that Rev-erbβ was recruited to the Srebp-1c promoter. Moreover, Rev-erbβ trans-activated the Srebp-1c promoter, in contrast, Rev-erbβ efficiently repressed the Rev-erbα promoter, a previously characterized target gene. Finally, treatment with the Rev-erb agonist (hemin) (i) increased the trans-activation of the Srebp-1c promoter by Rev-erbβ; and (ii) increased Rev-erbβ and Srebp-1c mRNA expression. These data suggest that Rev-erbβ has the potential to activate gene expression, and is a positive regulator of Srebp-1c, a regulator of lipogenesis.