Insulin-like growth factor binding protein-3. Organization of the human chromosomal gene and demonstration of promoter activity.

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.     

茶尺蠖核型多角体病毒多角体蛋白基因核苷酸序列及其在Baculoviridae中的地位(英文)

茶尺蠖核型多角体病毒（ＥｏＳＮＰＶ）基因组的ｐｏｌｈ和ｅｇｔ基因区约１４．２ｋｂ的酶切图谱被构建．ｅｇｔ基因位于ｐｏｌｈ基因上游约４．８ｋｂ处,但转录方向与ｐｏｌｈ基因相反．ＥｃｏＲⅤ－Ｌ片段ｐｏｌｈ基因及其旁侧的１１２５核苷酸序列被测定．ｐｏｌｈ基因编码区长７３８核苷酸,可编码２４６氨基酸的多肽．起始密码子ＡＴＧ上游是一个富含ＡＴ（ＡＴ占７１．２％）的启动子区,在－５２核苷酸处有杆状病毒晚期基因启动子转录起始基序ＡＴＡＡＧ．在终止密码子下游２０８核苷酸有一个ｐｏｌｙ（Ａ）信号,ＡＡＴＡＡＡ．但ＥｏＳＮＰＶｐｏｌｈ基因起始密码子ＡＴＧ相邻核苷酸序列为ＧＴＡＡＴＧＴ,其－３是个Ｇ,这与已知的１６种其它杆状病毒ｐｏｌｈ基因－３位置均是Ａ不相同．在分析了ＥｏＳＮＰＶ和ＨａＳＮＰＶ多角体蛋白基因核苷酸序列的基础上,通过ＭＡＬＩＧＮ程序,比较了目前已发表的２６种杆状病毒包涵体蛋白的序列,ＥｏＳＮＰＶ与黄杉毒蛾核型多角体病毒（ＯｐＳＮＰＶ）的同源性为最高,核苷酸序列的同源性为８３．０％,氨基酸序列达９４．７％;与其它２０种鳞翅目ＮＰＶ的同源性也很高,核苷酸序列同源性为７２．６％～８１．９％,氨基酸序列为８３．７％～９３     

Isolation and molecular cloning of insulin-like growth factor-binding protein-6.

Insulin-like growth factors (IGFs) together with their binding proteins (BPs) are potential regulators of folliculogenesis in mammalian ovary. To identify the various species of IGFBPs present in the ovary, we have undertaken a comprehensive purification scheme using gel filtration, ligand-affinity chromatography, and several steps of reverse phase HPLC to isolate all of the BPs in pig ovarian follicular fluid. Our effort yielded five distinct IGFBPs, and upon analysis, they were found to correspond to the previously identified human and rat IGFBP-2, -3, -4, -5, and -6. IGFBP-1 was not found in the pig ovarian follicular fluid under our experimental procedure. Of the six known classes of IGFBPs, the complete primary structures of the first five have been determined, but not IGFBP-6. Using amino acid sequence information from a tryptic fragment of pig IGFBP-6 to prepare a probe, cDNA clones encoding rat and human IGFBP-6 have been isolated and characterized. The deduced amino acid sequence revealed that rat IGFBP-6 contains 201 amino acids with a calculated mol wt of 21,461, while the human homolog contains 216 amino acids with a calculated mol wt of 22,847. In addition, a distinctive feature of human and rat IGFBP-6 is that they lack, respectively, two and four of the 18 homologous cysteines that are present in all other five IGFBPs. The missing cysteines in IGFBP-6 resulted in the absence of the invariant Gly-Cys-Gly-Cys-Cys sequence in the amino-terminal region of the molecule. Human IGFBP-6 possesses a single Asn-linked glycosylation site near the carboxyl-terminal, whereas no potential Asn-linked glycosylation sites are present in the rat sequence. A single 1.3-kilobase IGFBP-6 mRNA was detected by Northern analysis in all rat tissues examined, including testis, intestine, adrenal, kidney, stomach, spleen, heart, lung, brain, and liver, indicating that this BP is a ubiquitous protein. The chromosome location of the IGFBP-6 gene in human has been determined using polymerase chain reaction on somatic cell hybrid DNAs of human and hamster, and the results showed that it is located on chromosome 12.     

Genomic characterization of the human and mouse protein tyrosine phosphatase-1B genes

PTP-1B is a ubiquitously expressed intracellular protein tyrosine phosphatase (PTP) that has been implicated in the negative regulation of insulin signaling. Mice deficient in PTP-1B were found to have an enhanced insulin sensitivity and a resistance to diet-induced obesity. Interestingly, the human PTP-1B gene maps to chromosome 20 q13.1 in a region that has been associated with diabetes and obesity. Although there has been a partial characterization of the 3′ end of the human PTP-1B gene, the complete gene organization has not been described. In order to further characterize the PTP-1B gene, we have cloned and determined the genomic organization for both the human and mouse PTP-1B genes including the promoter. The human gene spans >74 kb and features a large first intron of >54 kb; the mouse gene likewise contains a large first intron, although the exact size has not been determined. The organization of the human and mouse PTP-1B genes is identical except for an additional exon at the 3′ end of the human that is absent in the mouse. The mouse PTP-1B gene maps to the distal arm of mouse chromosome 2 in the region H2-H3. This region is associated with a mouse obesity quantitiative trait locus (QTL) and is syntenic with human chromosome 20. The promoter region of both the human and mouse genes contain no TATA box but multiple GC-rich sequences that contain a number of consensus SP-1 binding sites. The basal activity of the human PTP-1B promoter was characterized in Hep G2 cells using up to 8 kb of 5′ flanking sequence. A 432 bp promoter construct immediately upstream of the ATG was able to confer maximal promoter activity. Within this sequence, there are at least three GC-rich sequences and one CCAAT box, and deletion of any of these elements results in decreased promoter activity. In addition, the promoter in a number of mouse strains contains, 3.5 kb upstream of the start codon, an insertion of an intracisternal a particle (IAP) element that possibly could alter the expression of PTP-1B mRNA in these strains.