DNA methylation contributes to expression of the human neurotensin/neuromedin N gene
DNA methylation contributes to expression of the human neurotensin/neuromedin N gene
复制标题
DOI：
10.1152/ajpgi.1998.274.3.g535
复制
发表时间：
1998-03-01
影响因子：
4.5
通讯作者：
Evers, BM
中科院分区：
文献类型：
--
作者：
Dong, ZZ;Wang, XF;Evers, BM
肠道和肝脏有一个共同的胚胎起源。编码肠道激素神经紧张素/神经素N （NT/N）的基因在成人小肠中表达，NT/N在胎儿肝脏中短暂表达，在成人肝脏中被抑制，并在某些肝癌中重新表达。在我们目前的研究中，我们发现NT/N基因在人肝癌细胞系Hep 3B中高水平表达，而在Hep G2细胞中不表达。为了进一步确定调控NT/N表达的机制，我们进行了Southern blotting和基因克隆技术。NT/N基因的改变和突变都不是导致NT/N差异表达模式的原因。将人NT/N启动子转染到Hep 3B或Hep G2中。这两种细胞系都支持NT/N转录，表明Hep G2细胞中NT/N表达缺失是由于缺乏阳性转录因子以外的机制。接下来评估了DNA甲基化的作用。体外NT/N启动子甲基化导致启动子活性降低67倍，而去甲基化剂5-氮杂胞苷在Hep G2细胞中诱导NT/N表达，提示DNA甲基化在肠道内分泌基因NT/N的表达中起作用。确定这些肝源性细胞系中NT/N表达的调节机制不仅可以更好地理解肠道内分泌基因的细胞特异性和发育调节，还可以深入了解肝细胞谱系模式和某些肝细胞癌的起源。
The gut and Liver share a common embryological origin. The gene encoding the gut hormone neurotensin/neuromedin N (NT/N) is expressed in the adult small bowel, and NT/N is transiently expressed in the fetal liver, suppressed in the adult liver, and reexpressed in certain liver cancers. In our present study, we found that the NT/N gene was expressed at high levels in the human hepatoma cell line Hep 3B but was not expressed in Hep G2 cells. To further determine the mechanisms regulating NT/N expression, we performed Southern blotting and gene cloning techniques. Neither alteration nor mutation of the NT/N gene was responsible for this differential NT/N expression pattern. Human NT/N promoter constructs were transfected into either Hep 3B or Hep G2. Both cell lines supported NT/N transcription, indicating that the absence of NT/N expression in Hep G2 cells was due to mechanisms other than the absence of positive transcription factors. The role of DNA methylation was next assessed. Methylation of NT/N promoter constructs in vitro resulted in a 67-fold reduction in promoter activity, whereas treatment with the demethylating agent 5-azacytidine induced NT/N expression in Hep G2 cells, thus suggesting that DNA methylation plays a role in the expression of the gut endocrine gene NT/N. Defining the mechanisms regulating NT/N expression in these hepatic-derived cell lines will provide not only a better understanding of cell-specific and developmental regulation of a gut endocrine gene but also possible insight into liver cell lineage patterns and the derivation of certain hepatocellular cancers.