Sumoylated PPARα mediates sex-specific gene repression and protects the liver from estrogen-induced toxicity in mice
Nicolas Leuenberger, Sylvain Pradervand, Walter Wahli
Nicolas Leuenberger, Sylvain Pradervand, Walter Wahli
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Research Article Genetics

Sumoylated PPARα mediates sex-specific gene repression and protects the liver from estrogen-induced toxicity in mice

Abstract

As most metabolic studies are conducted in male animals, understanding the sex specificity of the underlying molecular pathways has been broadly neglected; for example, whether PPARs elicit sex-dependent responses has not been determined. Here we show that in mice, PPARα has broad female-dependent repressive actions on hepatic genes involved in steroid metabolism and immunity. In male mice, this effect was reproduced by the administration of a synthetic PPARα ligand. Using the steroid oxysterol 7α-hydroxylase cytochrome P450 7b1 (Cyp7b1) gene as a model, we elucidated the molecular mechanism of this sex-specific PPARα-dependent repression. Initial sumoylation of the ligand-binding domain of PPARα triggered the interaction of PPARα with GA-binding protein α (GABPα) bound to the target Cyp7b1 promoter. Histone deacetylase and DNA and histone methylases were then recruited, and the adjacent Sp1-binding site and histones were methylated. These events resulted in loss of Sp1-stimulated expression and thus downregulation of Cyp7b1. Physiologically, this repression conferred on female mice protection against estrogen-induced intrahepatic cholestasis, the most common hepatic disease during pregnancy, suggesting a therapeutic target for prevention of this disease.

Authors

Nicolas Leuenberger, Sylvain Pradervand, Walter Wahli

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Figure 6

PPARα regulates epigenetic modification at the CYP7B1 promoter.

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PPARα regulates epigenetic modification at the CYP7B1 promoter. (A) ...
(A) QPCR shows that CYP7B1 is activated in human hepatic cells (HepG2) treated with the Dnmt inhibitor 5-aza-dC (10 and 50 μM) for 4 days. (B) NIH 3T3 cells treated with WY-14643 and increasing concentrations of 5-aza-dC (10 and 50 μM) were transfected with a PSG5-mouse PPARα expression vector (PPARα) or the empty vector (control). (C) QPCR shows that knockdown of Dnmt3L, but not Dnmt1, stimulated CYP7B1 in HepG2 cells. (D) Knockdown of Dnmt3L, but not Dnmt1, abolishes PPARα repression of CYP7B1. (E) Hepatic genomic DNA was treated with bisulfite and the Sp1 site methylation level recorded. (F) After knockdown of human PPARα in HepG2 cells, Sp1 site methylation level was recorded and compared with CYP7B1 expression. Cells in D and F were treated with WY-14643 for 48 hours. In A–D and F, values are presented as mean ± SEM (n = 3). *P ≤ 0.05, **P ≤ 0.01 versus control. (G) In vivo binding of Sp1 to the Cyp7b1 promoter was detected by a ChiP assay of hepatic nuclear proteins using Sp1 antibody. Primers encompassing the GABPα and Sp1 binding sites were used for PCR. Treated, WY-14643; Control, untreated.