Pachnis V, Brannan C I, Tilghman S M
Department of Molecular Biology, Princeton University, NJ 08544.
EMBO J. 1988 Mar;7(3):673-81. doi: 10.1002/j.1460-2075.1988.tb02862.x.
We report the cloning and sequence determination of the mouse H19 gene. This gene is under the genetic control of two trans-acting loci in the mouse, termed raf and Rif. These loci determine the adult basal and inducible levels, respectively, of H19 mRNA, as well as the mRNA for alpha-fetoprotein. By elucidating the sequence and structure of the H19 gene we show that it is unrelated to the alpha-fetoprotein gene, and therefore must have acquired its regulation by raf and Rif independently. The sequence also indicates that the H19 gene has a very unusual structure. It is composed of five exons, 1307, 135, 119, 127 and 560 bp in size, along with four very small introns whose combined lengths are 270 bases. The largest open reading frame of the gene, sufficient to encode a protein of approximately 14 kd, is contained entirely within the first large exon, 680 bases downstream of the cap site of the mRNA. Preceding the translation initiation codon are four ATG codons, each of which is followed shortly thereafter by translation terminator codons. The rest of the gene, which encompasses all five exons, is presumed to be untranslated. That the long 5' untranslated region may be used to regulate the translation of the mRNA is suggested from in vitro translation studies. Experiments which utilized tissue culture cell lines of the mesodermal lineage suggest that the gene is activated very early during muscle cell differentiation.
我们报道了小鼠H19基因的克隆及序列测定。该基因受小鼠中两个反式作用位点raf和Rif的遗传控制。这些位点分别决定了H19 mRNA以及甲胎蛋白mRNA在成年小鼠中的基础水平和诱导水平。通过阐明H19基因的序列和结构，我们发现它与甲胎蛋白基因无关，因此其受raf和Rif调控的机制必定是独立获得的。序列分析还表明，H19基因具有非常独特的结构。它由五个外显子组成，大小分别为1307、135、119、127和560 bp，还有四个非常小的内含子，其总长度为270个碱基。该基因最大的开放阅读框足以编码一个约14 kd的蛋白质，它完全包含在第一个大外显子中，位于mRNA帽位点下游680个碱基处。在翻译起始密码子之前有四个ATG密码子，每个密码子之后紧接着就是翻译终止密码子。基因的其余部分包括所有五个外显子，推测为非翻译区。体外翻译研究表明，长5'非翻译区可能用于调控mRNA的翻译。利用中胚层谱系的组织培养细胞系进行的实验表明，该基因在肌肉细胞分化早期就被激活。
