Imai Satoki, Kikuchi Ryota, Kusuhara Hiroyuki, Yagi Shintaro, Shiota Kunio, Sugiyama Yuichi
Department of Molecular Pharmacokinetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
Mol Pharmacol. 2009 Mar;75(3):568-76. doi: 10.1124/mol.108.052589. Epub 2008 Dec 1.
Tissue-specific expression of transporters is tightly linked with their physiological functions through the regulation of the membrane transport of their substrates. We hypothesized that epigenetic regulation underlies the tissue-specific expression of mouse liver-specific transporters (Oatp1b2/Slco1b2, Ntcp/Slc10a1, Bsep/Abcb11, and Abcg5/g8). We examined their DNA methylation and histone modification profiles near the transcriptional start site (TSS) in the liver, kidney, and cerebrum. Genome-wide DNA methylation profiling with tissue-dependent differentially methylated region profiling with restriction tag-mediated amplification and subsequent bisulfite genomic sequencing demonstrated that the CpG dinucleotides around the TSS of Oatp1b2 (from -515 to +149 CpGs), Ntcp (from -481 to +495 CpGs), Bsep (from -339 to +282 CpGs), and Abcg5/g8 (from -161 to +5 CpGs for Abcg5, i.e., from -213 to -48 CpGs for Abcg8) were hypomethylated in the liver and hypermethylated in the kidney and cerebrum. The opposite pattern was observed for Pept2/Slc15a2 (from -638 to +4 CpGs), which was expressed in the kidney and cerebrum but not in the liver. These DNA methylation profiles are consistent with the tissue distribution of these transporters. A chromatin immunoprecipitation assay demonstrated that the histone H3 associated with Oatp1b2, Ntcp, Bsep, and Abcg5/g8 promoters was hyperacetylated in the liver but was acetylated very little in the kidney and cerebrum, whereas the upstream region of Pept2 was hyperacetylated only in the kidney and cerebrum. These results suggest the involvement of epigenetic systems in the tissue-specific expression of mouse transporters Oatp1b2, Ntcp, Bsep, Abcg5/g8, and Pept2.
转运蛋白的组织特异性表达通过对其底物膜转运的调节与其生理功能紧密相连。我们推测表观遗传调控是小鼠肝脏特异性转运蛋白（Oatp1b2/Slco1b2、Ntcp/Slc10a1、Bsep/Abcb11和Abcg5/g8）组织特异性表达的基础。我们检测了它们在肝脏、肾脏和大脑中转录起始位点（TSS）附近的DNA甲基化和组蛋白修饰谱。通过限制标签介导的扩增进行全基因组DNA甲基化分析以及随后的亚硫酸氢盐基因组测序，结果表明，Oatp1b2（从 -515至 +149个CpG）、Ntcp（从 -481至 +495个CpG）、Bsep（从 -339至 +282个CpG）和Abcg5/g8（Abcg5为从 -161至 +5个CpG，即Abcg8为从 -213至 -48个CpG）TSS周围的CpG二核苷酸在肝脏中低甲基化，在肾脏和大脑中高甲基化。在肾脏和大脑中表达但在肝脏中不表达的Pept2/Slc15a2（从 -638至 +4个CpG）呈现相反的模式。这些DNA甲基化谱与这些转运蛋白的组织分布一致。染色质免疫沉淀分析表明，与Oatp1b2、Ntcp、Bsep和Abcg5/g8启动子相关的组蛋白H3在肝脏中高度乙酰化，但在肾脏和大脑中乙酰化程度很低，而Pept2的上游区域仅在肾脏和大脑中高度乙酰化。这些结果表明表观遗传系统参与了小鼠转运蛋白Oatp1b2、Ntcp、Bsep、Abcg5/g8和Pept2的组织特异性表达。
