Kaneoka Hidenori, Miyake Katsuhide, Iijima Shinji
Department of Biotechnology, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan.
Biochem Biophys Res Commun. 2009 Oct 2;387(4):717-22. doi: 10.1016/j.bbrc.2009.07.095. Epub 2009 Jul 24.
The gene for tryptophan oxygenase (TO) is expressed in adult hepatocytes in a tissue- and differentiation-specific manner. The TO promoter has two glucocorticoid-responsive elements (GREs), and its expression is regulated by glucocorticoid hormone in the liver. We found a novel GRE in close proximity to a scaffold/matrix attachment region (S/MAR) that was located around -8.5kb from the transcriptional start site of the TO gene by electrophoretic mobility shift and chromatin immunoprecipitation (ChIP) assays. A combination of nuclear fractionation and quantitative PCR analysis showed that the S/MAR was tethered to the nuclear matrix in both fetal and adult hepatocytes. ChIP assay showed that, in adult hepatocytes, the S/MAR-GRE and the promoter proximal regions interacted with lamin and heterogeneous nuclear ribonucleoprotein U in a dexamethasone dependent manner, but this was not the case in fetal cells, suggesting that developmental stage-specific expression of the TO gene might rely on the binding of the enhancer (the -8.5kb S/MAR-GRE) and the promoter to the inner nuclear matrix.
色氨酸加氧酶（TO）基因在成年肝细胞中以组织和分化特异性方式表达。TO启动子有两个糖皮质激素反应元件（GREs），其表达在肝脏中受糖皮质激素调节。通过电泳迁移率变动分析和染色质免疫沉淀（ChIP）试验，我们在距离TO基因转录起始位点约-8.5kb处发现了一个与支架/基质附着区域（S/MAR）紧邻的新型GRE。细胞核分级分离和定量PCR分析相结合表明，S/MAR在胎儿和成年肝细胞中均与核基质相连。ChIP试验表明，在成年肝细胞中，S/MAR-GRE和启动子近端区域以地塞米松依赖的方式与核纤层蛋白和不均一核核糖核蛋白U相互作用，但在胎儿细胞中并非如此，这表明TO基因的发育阶段特异性表达可能依赖于增强子（-8.5kb S/MAR-GRE）和启动子与内核基质的结合。
