Fig. 4

Regulation of CHRNA4 by HNF4 and RXRA. a HNF4A (top) and RXRA (bottom) are highly expressed in human liver as compared to other human tissues. The Y-axis indicates expression level (RPKM) measured by RNA-seq data from the GTEx project. The tissues are ranked by median expression of HNF4A and RXRA. b Evolutionarily conserved epigenetic landscape and transcriptional pattern of Chrna4 in mouse and human liver. The liver-specific promoter (blue-shade), which is located ~4.8 KB upstream of the RefSeq promoter, is enriched for strong, active histone modifications and RNA polymerase II ChIP-seq signal (Pol2). The CAGE-seq signal of liver indicates Chrna4 is predominantly transcribed in hepatocyte from the liver-specific promoter P2. Available ChIP-seq data indicate that HNF4A/Hnf4a and RXRA/Rxra directly bind to the liver-specific promoter of CHRNA4 /Chrna4 in human and mouse liver, respectively