Su Jih-Shyun, Tsai Ting-Fen, Chang Hua-Mei, Chao Kun-Mao, Su Tsung-Sheng, Tsai Shih-Feng
Faculty of Life Sciences and Institute of Genetics, National Yang-Ming University, Taipei 112.
J Biol Chem. 2006 Jul 21;281(29):19809-21. doi: 10.1074/jbc.M603638200. Epub 2006 May 4.
Gene duplication and divergence have contributed to the biochemical diversity of the alcohol dehydrogenase (ADH) family. Class I ADH is the major enzyme that catalyzes alcohol to acetaldehyde in the liver. To investigate the mechanism(s) controlling tissue-specific and temporal regulation of the three human class I ADH genes (ADH1A, ADH1B, and ADH1C), we compared genomic sequences for the human and mouse ADH loci and analyzed human ADH gene expression in BAC transgenic mice carrying different lengths of the upstream sequences of the class I ADH. A conserved noncoding sequence, located between the class I and class IV ADH (ADH7) genes, was found to be essential for directing class I ADH gene expression in fetal and adult livers. Within this region, a 275-bp fragment displaying liver-specific DNase I hypersensitivity was bound by HNF1. The HNF1-containing upstream sequence enhanced all three class I ADH promoters in an orientation-dependent manner, and the transcriptional activation depended on binding to the HNF1 site. Deletion of the conserved HNF1 site in the BAC led to the shutdown of human class I ADH gene expression in the transgenic livers, leaving ADH1C gene expression in the stomach unchanged. Moreover, interaction between the upstream element and the class I ADH gene promoters was demonstrated by chromosome conformation capture, suggesting a DNA looping mechanism is involved in gene activation. Taken together, our data indicate that HNF1 binding, at approximately 51 kb upstream, plays a master role in controlling human class I ADH gene expression and may govern alcohol metabolism in the liver.
基因复制和分化促成了乙醇脱氢酶（ADH）家族的生化多样性。I类ADH是肝脏中催化酒精转化为乙醛的主要酶。为了研究控制人类三个I类ADH基因（ADH1A、ADH1B和ADH1C）组织特异性和时间调控的机制，我们比较了人类和小鼠ADH基因座的基因组序列，并分析了携带不同长度I类ADH上游序列的BAC转基因小鼠中的人类ADH基因表达。发现位于I类和IV类ADH（ADH7）基因之间的一个保守非编码序列对于指导胎儿和成年肝脏中的I类ADH基因表达至关重要。在该区域内，一个显示肝脏特异性DNase I超敏性的275 bp片段被HNF1结合。含有HNF1的上游序列以方向依赖的方式增强了所有三个I类ADH启动子，转录激活依赖于与HNF1位点的结合。BAC中保守的HNF1位点的缺失导致转基因肝脏中人类I类ADH基因表达的关闭，而胃中ADH1C基因的表达保持不变。此外，通过染色体构象捕获证明了上游元件与I类ADH基因启动子之间的相互作用，表明DNA环化机制参与了基因激活。综上所述，我们的数据表明，上游约51 kb处的HNF1结合在控制人类I类ADH基因表达中起主要作用，并且可能调控肝脏中的酒精代谢。
