6C). These results are consistent with decreased mRNA levels (Fig. 4A) and decreased occupancy of RNAPII and acetylated H3 levels at

those genes (Fig. 5C-F). Collectively, these studies suggest that a large fraction of the agonist-activated FXR target genes examined is directly repressed. Because FXR was shown to increase its target genes in nearly all previous studies and to repress some target genes indirectly through the induction of SHP,3, 4, 11, 14 our finding that direct gene repression by FXR is common is unexpected. In this study, ChIP-seq analysis of hepatic genomic binding of agonist-activated FXR in healthy and obese mice resulted Selleckchem Sotrastaurin Dasatinib concentration in two major findings. First, of the total hepatic FXR-binding sites, nearly half of the sites were unique to healthy or obese mice, implying altered FXR transcriptional signaling in obesity. Second, further analyses utilizing ChIP and qRT-PCR assays suggested that a large fraction of FXR target genes examined are directly repressed by ligand-activated FXR. Approximately 80% of identified FXR-binding sites are localized in intergenic and intron regions, at a consensus IR1 motif, in healthy and obese mice. These findings are consistent

with recently reported ChIP-seq analysis of FXR binding in healthy

mice.26-28 Thomas et al., for the first time, identified and compared genomic FXR-binding sites in liver and intestine in mice treated with GW4064. Interestingly, only 11% of total FXR-binding sites were shared between liver and intestine, demonstrating tissue-specific FXR target genes.26 Chong et al. identified FXR-binding sites in mouse hepatic chromatin, and showed that binding sites for liver receptor homolog 1 (LRH-1) were enriched near the asymmetric IR1 FXR site and that LRH-1 and FXR can coactivate gene expression.27 Lee et al. also identified functional FXR sites within promoters, introns, 上海皓元医药股份有限公司 or intragenic regions of selected genes involved in xenobiotic metabolism, suggesting a role for FXR in liver protection against toxic substances, such as acetaminophen.28 This current study reveals numerous previously unknown potential FXR target genes unique in healthy and obese mice and categorization of these genes identifies new functions, suggesting that biological pathways potentially regulated by FXR are altered in obesity. We have shown that acetylation of FXR inhibits DNA binding of the FXR/RXRα heterodimer, and that FXR acetylation levels are highly elevated in obese mice.