Takayama Y, Rand-Weaver M, Kawauchi H, Ono M
Department of Molecular Biology, School of Medicine, Kitasato University, Kanagawa, Japan.
Mol Endocrinol. 1991 Jun;5(6):778-86. doi: 10.1210/mend-5-6-778.
From a chum salmon genomic DNA library, clones coding for somatolactin (SL), a presumed pituitary hormone belonging to the GH/PRL family, were isolated and analyzed. The salmon SL gene was 16 kilobases (kb) in length, this being the largest among mammalian GH (approximately 2 kb) and PRL (approximately 10 kb) and fish GH (approximately 4 kb) genes. As in the case of mammalian GH/PRL genes, the salmon SL gene was comprised of five exons in contrast to rainbow trout and Atlantic salmon GH genes, which each have six exons. Upstream from the transcriptional initiation site were found one TATA box identical to those of mammalian PRL genes and four consensus sequences corresponding to the Pit-1/GHF-1 binding element which is essential to the expression of mammalian GH and/or PRL genes. The similarity in amino acid sequences and organization of the SL gene with mammalian GH/PRL genes indicates that the SL gene is quite likely produced from an ancestral gene common to GH/PRL genes by gene duplication. Based on these considerations, an evolutionary model for the GH/PRL/SL gene family was made and shows the common ancestral gene to originate not from duplication of a primordial gene but from shuffling of independent exons and a regulatory sequence.
从银大麻哈鱼基因组DNA文库中，分离并分析了编码生长催乳素（SL）的克隆，生长催乳素是一种假定的属于生长激素/催乳素家族的垂体激素。大麻哈鱼SL基因长度为16千碱基（kb），这在哺乳动物生长激素（约2 kb）、催乳素（约10 kb）以及鱼类生长激素（约4 kb）基因中是最大的。与哺乳动物生长激素/催乳素基因一样，大麻哈鱼SL基因由五个外显子组成，而虹鳟和大西洋鲑生长激素基因各有六个外显子。在转录起始位点上游，发现了一个与哺乳动物催乳素基因相同的TATA框，以及四个与Pit-1/GHF-1结合元件相对应的共有序列，该元件对哺乳动物生长激素和/或催乳素基因的表达至关重要。SL基因与哺乳动物生长激素/催乳素基因在氨基酸序列和结构上的相似性表明，SL基因很可能是通过基因复制从生长激素/催乳素基因的共同祖先基因产生的。基于这些考虑，构建了生长激素/催乳素/SL基因家族的进化模型，该模型表明共同祖先基因并非起源于原始基因的复制，而是起源于独立外显子和调控序列的重排。
