A heparin-binding growth factor secreted by macrophage-like cells that is related to EGF.

Macrophage-like U-937 cells secrete a 22-kilodalton heparin-binding growth factor that is mitogenic for BALB-3T3 fibroblasts and smooth muscle cells, but not endothelial cells. The amino acid sequence predicted from complementary DNA clones indicates that the mitogen is a new member of the epidermal growth factor (EGF) family. This heparin-binding EGF-like growth factor (HB-EGF) binds to EGF receptors on A-431 epidermoid carcinoma cells and smooth muscle cells, but is a far more potent mitogen for smooth muscle cells than is EGF. HB-EGF is also expressed in cultured human macrophages and may be involved in macrophage-mediated cellular proliferation.     

Identification and characterization of the protein encoded by the human N-myc oncogene

The human N-myc gene is related to the c-myc proto-oncogene, and has been shown to have transforming potential in vitro. Many studies have reported amplification of N-myc in human neuroblastoma and retinoblastoma cell lines. In primary tumors, amplification of the gene was found to correlate directly with behavior of the tumor. Specific restriction fragments of a partial complementary DNA clone of N-myc from LA-N-5 human neuroblastoma cells were placed into a bacterial expression vector for the purpose of producing antigens representative of the N-myc protein. Rabbits immunized with these antigens produced antisera that recognized a protein of 62-64 kilodaltons in neuroblastoma cells. By several criteria, this protein appears to be part of the same proto-oncogene family as the c-myc protein. Moreover, the antisera to fragments of this protein were capable of histochemically identifying malignant cells in clinical specimens.     

Gene for human insulin receptor: localization to site on chromosome 19 involved in pre-B-cell leukemia

Consistent chromosomal translocations in neoplastic cells may alter the expression of proto-oncogenes that are located near the breakpoints. The complementary DNA sequence of the human insulin receptor is similar to those of the EGF receptor (erbB oncogene) and products of the src family of oncogenes. With in situ hybridization and Southern blot analysis of somatic cell hybrid DNA, the human insulin receptor gene was mapped to the distal short arm of chromosome 19 (bands p13.2----p13.3), a site involved in a nonrandom translocation in pre-B-cell acute leukemia.     

Production of an epidermal growth factor receptor-related protein

Human epidermoid carcinoma A431 cells in culture produce a soluble 105-kilodalton protein which, by the criteria of epidermal growth factor (EGF) binding, recognition by monoclonal and polyclonal antibodies to the EGF receptor, amino-terminal sequence analysis and carbohydrate content, is related to the cell surface domain of the EGF receptor. The high rate of production and the finding that with biosynthetic labeling the specific activity of this 105-kilodalton protein exceeds that of the intact receptor indicate that it is not derived from membrane-bound mature receptor but is separately produced by the cell. These cells thus separately synthesize an EGF receptor that is inserted into the membrane and an EGF receptor-related protein that is secreted.     

The neu gene: an erbB-homologous gene distinct from and unlinked to the gene encoding the EGF receptor

The neu oncogene, identified in ethylnitrosourea-induced rat neuroglioblastomas, had strong homology with the erbB gene that encodes the epidermal growth factor receptor. This homology was limited to the region of erbB encoding the tyrosine kinase domain. It was concluded that the neu gene is a distinct novel gene, as it is not coamplified with sequences encoding the EGF receptor in the genome of the A431 tumor line and it maps to human chromosome 17.     

Blocking of EGF-dependent cell proliferation by EGF receptor kinase inhibitors

A systematic series of low molecular weight protein tyrosine kinase inhibitors were synthesized; they had progressively increasing affinity over a 2500-fold range toward the substrate site of epidermal growth factor (EGF) receptor kinase domain. These compounds inhibited EGF receptor kinase activity up to three orders of magnitude more than they inhibited insulin receptor kinase, and they also effectively inhibited the EGF-dependent autophosphorylation of the receptor. The most potent compounds effectively inhibited the EGF-dependent proliferation of A431/clone 15 cells with little or no effect on the EGF-independent proliferation of these cells. The potential use of tyrosine protein kinase inhibitors as antiproliferative agents is demonstrated.     

Chromosomal location of human T-cell receptor gene Ti beta

A complementary DNA probe corresponding to the beta-chain gene of Ti, the human T lymphocyte receptor, has been molecularly cloned. The chromosomal origin of the Ti beta gene was determined with the complementary DNA by screening a series of 12 cell hybrid (mouse X human) DNA's containing overlapping subsets of human chromosomes. DNA hybridization (Southern) experiments showed that the human Ti beta gene resides on chromosome 7 and is thus not linked to the immunoglobulin loci or to the major histocompatibility locus in humans.     

Sequence and expression of human estrogen receptor complementary DNA

The mechanism by which the estrogen receptor and other steroid hormone receptors regulate gene expression in eukaryotic cells is not well understood. In this study, a complementary DNA clone containing the entire translated portion of the messenger RNA for the estrogen receptor from MCF-7 human breast cancer cells was sequenced and then expressed in Chinese hamster ovary (CHO-K1) cells to give a functional protein. An open reading frame of 1785 nucleotides in the complementary DNA corresponded to a polypeptide of 595 amino acids and a molecular weight of 66,200, which is in good agreement with published molecular weight values of 65,000 to 70,000 for the estrogen receptor. Homogenates of transformed Chinese hamster ovary cells containing a protein that bound [3H]estradiol and sedimented as a 4S complex in salt-containing sucrose gradients and as an 8 to 9S complex in the absence of salt. Interaction of this receptor-[3H]estradiol complex with a monoclonal antibody that is specific for primate ER confirms the identity of the expressed complementary DNA as human estrogen receptor. Amino acid sequence comparisons revealed significant regional homology among the human estrogen receptor, the human glucocorticoid receptor, and the putative v-erbA oncogene product. This suggests that steroid receptor genes and the avian erythroblastosis viral oncogene are derived from a common primordial gene. The homologous region, which is rich in cysteine, lysine, and arginine, may represent the DNA-binding domain of these proteins.     

Epidermal-growth-factor-dependent transformation by a human EGF receptor proto-oncogene

The epidermal growth factor (EGF) receptor gene EGFR has been placed in a retrovirus vector to examine the growth properties of cells that experimentally overproduce a full-length EGF receptor. NIH 3T3 cells transfected with the viral DNA or infected with the corresponding rescued retrovirus developed a fully transformed phenotype in vitro that required both functional EGFR expression and the presence of EGF in the growth medium. Cells expressing 4 x 10(5) EGF receptors formed tumors in nude mice, while control cells did not. Therefore, the EGFR retrovirus, which had a titer on NIH 3T3 cells that was greater than 10(7) focus-forming units per milliliter, can efficiently transfer and express this gene, and increased numbers of EGF receptors can contribute to the transformed phenotype.     

Engineering herbicide tolerance in transgenic plants

The herbicide glyphosate is a potent inhibitor of the enzyme 5-enolpyruvylshikimate- 3-phosphate (EPSP) synthase in higher plants. A complementary DNA (cDNA) clone encoding EPSP synthase was isolated from a complementary DNA library of a glyphosate-tolerant Petunia hybrida cell line (MP4-G) that overproduces the enzyme. This cell line was shown to overproduce EPSP synthase messenger RNA as a result of a 20-fold amplification of the gene. A chimeric EPSP synthase gene was constructed with the use of the cauliflower mosaic virus 35S promoter to attain high level expression of EPSP synthase and introduced into petunia cells. Transformed petunia cells as well as regenerated transgenic plants were tolerant to glyphosate.     

Identification of a novel thyroid hormone receptor expressed in the mammalian central nervous system

A complementary DNA clone derived from rat brain messenger RNA has been isolated on the basis of homology to the human thyroid hormone receptor gene. Expression of this complementary DNA produces a high-affinity binding protein for thyroid hormones. Sequence analysis and the mapping of this gene to a distinct human genetic locus indicate the existence of multiple human thyroid hormone receptors. Messenger RNA from this gene is expressed in a tissue-specific fashion with highest levels in the central nervous system.     

Interferon-beta-related DNA is dispersed in the human genome

Interferon-beta 1 (IFN-beta 1) complementary DNA was used as a hybridization probe to isolate human genomic DNA clones lambda B3 and lambda B4 from a human genomic DNA library. Blot-hybridization procedures and partial nucleotide sequencing revealed that lambda B3 is related to IFN-beta 1 (and more distantly to IFN-alpha 1). Analyses of DNA obtained from a panel of human-rodent somatic cell hybrids that were probed with DNA derived from lambda B3 showed that lambda B3 is on human chromosome 2. Similar experiments indicated that lambda B4 is not on human chromosomes 2, 5, or 9. The finding that DNA related to the IFN-beta 1 gene (and IFN-alpha 1 gene) is dispersed in the human genome raises new questions about the origins of the interferon genes.     

Cloning of human androgen receptor complementary DNA and localization to the X chromosome

The androgen receptor (AR) mediates the actions of male sex steroids. Human AR genomic DNA was cloned from a flow-sorted human X chromosome library by using a consensus nucleotide sequence from the DNA-binding domain of the family of nuclear receptors. The AR gene was localized on the human X chromosome between the centromere and q13. Cloned complementary DNA, selected with an AR-specific oligonucleotide probe, was expressed in monkey kidney (COS) cells and yielded a high-affinity androgen-binding protein with steroid-binding specificity corresponding to that of native AR. A predominant messenger RNA species of 9.6 kilobases was identified in human, rat, and mouse tissues known to contain AR and was undetectable in tissues lacking AR androgen-binding activity, including kidney and liver from androgen-insensitive mice. The deduced amino acid sequence of AR within the DNA-binding domain has highest sequence identity with the progesterone receptor.     

Recombinant human granulocyte colony-stimulating factor: effects on normal and leukemic myeloid cells

Experiments were conducted to isolate and characterize the gene and gene product of a human hematopoietic colony-stimulating factor with pluripotent biological activities. This factor has the ability to induce differentiation of a murine myelomonocytic leukemia cell line WEHI-3B(D+) and cells from patients with newly diagnosed acute nonlymphocytic leukemia (ANLL). A complementary DNA copy of the gene encoding a pluripotent human granulocyte colony-stimulating factor (hG-CSF) was cloned and expressed in Escherichia coli. The recombinant form of hG-CSF is capable of supporting neutrophil proliferation in a CFU-GM assay. In addition, recombinant hG-CSF can support early erythroid colonies and mixed colony formation. Competitive binding studies done with 125I-labeled hG-CSF and cell samples from two patients with newly diagnosed human leukemias as well as WEHI-3B(D+) cells showed that one of the human leukemias (ANLL, classified as M4) and the WEHI-3B(D+) cells have receptors for hG-CSF. Furthermore, the murine WEHI-3B(D+) cells and human leukemic cells classified as M2, M3, and M4 were induced by recombinant hG-CSF to undergo terminal differentiation to macrophages and granulocytes. The secreted form of the protein produced by the bladder carcinoma cell line 5637 was found to be O-glycosylated and to have a molecular weight of 19,600.     

Chimeric NGF-EGF receptors define domains responsible for neuronal differentiation

To determine the domains of the low-affinity nerve growth factor (NGF) receptor required for appropriate signal transduction, a series of hybrid receptors were constructed that consisted of the extracellular ligand-binding domain of the human epidermal growth factor (EGF) receptor (EGFR) fused to the transmembrane and cytoplasmic domains of the human low-affinity NGF receptor (NGFR). Transfection of these chimeric receptors into rat pheochromocytoma PC12 cells resulted in appropriate cell surface expression. Biological activity mediated by the EGF-NGF chimeric receptor was assayed by the induction of neurite outgrowth in response to EGF in stably transfected cells. Furthermore, the chimeric receptor mediated nuclear signaling, as evidenced by the specific induction of transin messenger RNA, an NGF-responsive gene. Neurite outgrowth was not observed with chimeric receptors that contained the transmembrane domain from the EGFR, suggesting that the membrane-spanning region and cytoplasmic domain of the low-affinity NGFR are necessary for signal transduction.     

赛加羚羊的分子生物学鉴别

为了解决以往赛加羚羊(Saiga tatarica)鉴别方法存在的不确定性或分辨率低的问题,在mtDNA的12S rRNA基因易变区设计了2对赛加羚羊特异性引物Saiga A和Saiga B,通过PCR扩增和常规电泳检测,分别得到127 bp和320 bp的片段,进而可通过这两个片段的有无来特异性检出赛加羚羊的DNA。引物Saiga A和Saiga B的最小检出量为1．0 ng DNA,稳定性和特异性好、灵敏度很高,可以应用于赛加羚羊样品的检测。