Cubbage M L, Suwanichkul A, Powell D R
Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77054.
J Biol Chem. 1990 Jul 25;265(21):12642-9.
Insulin-like growth factor binding protein-3 (IGFBP-3) can modulate the mitogenic and metabolic effects of the insulin-like growth factors (IGFs). IGFBP-3 protein levels are developmentally regulated and influenced by a number of hormonal stimuli both in vitro and in vivo. As a first step toward understanding how hormonal and developmental factors regulate IGFBP-3 production, we are characterizing the human IGFBP-3 chromosomal gene and promoter. Southern analysis demonstrates a single copy of the IGFBP-3 gene in the human genome. This gene spans 8.9 kilobases; the protein-coding region is divided into four exons while a fifth exon contains the 3'-untranslated region. Primer extension studies locate the IGFBP-3 mRNA cap site 132 base pairs 5' to the ATG translation initiation codon. On the chromosomal gene, this cap site is located 30 base pairs 3' to the start of a TATA box and 97 base pairs 3' to a consensus GC upstream promoter element, an organization common to many eukaryotic promoters. When this potential IGFBP-3 promoter region is placed upstream to the chloramphenicol acetyltransferase reporter gene, it directs high-level production of chloramphenicol acetyltransferase in transfected COS-1 cells. These observations suggest an uncomplicated organization for the IGFBP-3 chromosomal gene and promoter in the human genome.
胰岛素样生长因子结合蛋白-3（IGFBP-3）可调节胰岛素样生长因子（IGFs）的促有丝分裂和代谢作用。IGFBP-3蛋白水平在发育过程中受到调控，并且在体外和体内均受到多种激素刺激的影响。作为了解激素和发育因子如何调节IGFBP-3产生的第一步，我们正在对人类IGFBP-3染色体基因和启动子进行表征。Southern分析表明，人类基因组中IGFBP-3基因有一个单拷贝。该基因跨度为8.9千碱基；蛋白质编码区分为四个外显子，而第五个外显子包含3'-非翻译区。引物延伸研究将IGFBP-3 mRNA帽位点定位在ATG翻译起始密码子上游132个碱基对处。在染色体基因上，该帽位点位于TATA盒起始处下游30个碱基对以及共有GC上游启动子元件下游97个碱基对处，这种结构在许多真核启动子中很常见。当将这个潜在的IGFBP-3启动子区域置于氯霉素乙酰转移酶报告基因上游时，它可在转染的COS-1细胞中指导氯霉素乙酰转移酶的高水平产生。这些观察结果表明，人类基因组中IGFBP-3染色体基因和启动子的结构并不复杂。
