Tyrosine kinase activity and transformation potency of bcr-abl oncogene products

Oncogenic activation of the proto-oncogene c-abl in human leukemias occurs as a result of the addition of exons from the gene bcr and truncation of the first abl exon. Analysis of tyrosine kinase activity and quantitative measurement of transformation potency in a single-step assay indicate that variation in bcr exon contribution results in a functional difference between p210bcr-abl and p185bcr-abl proteins. Thus, foreign upstream sequences are important in the deregulation of the kinase activity of the abl product, and the extent of deregulation correlates with the pathological effects of the bcr-abl proteins.     

A G protein gamma subunit shares homology with ras proteins

Guanine nucleotide binding proteins (G proteins) that transduce signals from cell surface receptors to effector molecules are made up of three subunits, alpha, beta, and gamma. A complementary DNA clone that encodes a 71-amino acid protein was isolated from bovine brain; this protein contains peptide sequences that were derived from the purified gamma subunit of Gi and Go. The primary sequence of this G protein gamma subunit (G gamma) has 55 percent homology to the gamma subunit of transducin (T gamma) and also has homology to functional domains of mammalian ras proteins. The probe for isolating the clone was generated with the use of the polymerase chain reaction (PCR). The extent of divergence between T gamma and G gamma, the isolation of homologous PCR-generated fragments, and the differences between the predicted amino acid sequence of G gamma and that derived from the gamma subunit of Gi and Go indicate that gamma subunits are encoded by a family of genes.     

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.     

Direct interaction of a ligand for the erbB2 oncogene product with the EGF receptor and p185erbB2

The erbB2 oncogene encodes a 185-kilodalton transmembrane protein whose sequence is similar to the epidermal growth factor receptor (EGFR). A 30-kilodalton factor (gp30) secreted from MDA-MB-231 human breast cancer cells was shown to be a ligand for p185erbB2. An antibody to EGFR abolished the tyrosine phosphorylation induced by EGF and transforming growth factor-alpha (TGF-alpha) but only partially blocked that produced by gp30 in SK-BR-3 breast cancer cells. In two cell lines that overexpress erbB2 but do not expresss EGFR (MDA-MB-453 breast cancer cells and a Chinese hamster ovary cell line that had been transfected with erbB2), phosphorylation of p185erbB2 was induced only by gp30. The gp30 specifically inhibited the growth of cells that overexpressed p185erbB2. An antibody to EGFR had no effect on the inhibition of SK-BR-3 cell colony formation obtained with gp30. Thus, it appeared that gp30 interacted directly with the EGFR and erbB2. Direct binding of gp30 to p185erbB2 was confirmed by binding competition experiments, where gp30 was found to displace the p185erbB2 binding of a specific antibody to p185erbB2. The evidence described here suggests that gp30 is a ligand for p185erbB2.     

EGF receptor and erbB-2 tyrosine kinase domains confer cell specificity for mitogenic signaling

The epidermal growth factor (EGF) receptor (EGFR) can efficiently couple with mitogenic signaling pathways when it is transfected into interleukin-3 (IL-3)-dependent 32D hematopoietic cells. When expression vectors for erbB-2, which is structurally related to EGFR, or its truncated counterpart, delta NerbB-2, were introduced into 32D cells, neither was capable of inducing proliferation. This was despite overexpression and constitutive tyrosine kinase activity of their products at levels associated with potent transformation of fibroblast target cells. Thus, EGFR and erbB-2 couple with distinct mitogenic signaling pathways. The region responsible for the specificity of intracellular signal transduction was localized to a 270-amino acid stretch encompassing their respective tyrosine kinase domains. Thus, tissue- or cell-specific regulation of growth factor receptor signaling can occur at a point after the initial interaction of growth factor with receptor. Such specificity in signal transduction may account for the selection of certain oncogenes in some malignancies.     

The EGF receptor kinase substrate p35 in the floor plate of the embryonic rat CNS

P35 is a calcium- and phospholipid-binding protein that was originally isolated as a substrate for the epidermal growth factor (EGF) receptor tyrosine kinase and later was found to be related to lipocortin I. Immunohistochemistry was used to localize p35 to a raphe of primitive glial ependymal cells in the median one-third of the floor plate in the central nervous system (CNS) of rat embryos. The p35 appears by embryonic day 12 before the arrival of pioneering ventral commissural axons. The unexpected, discrete distribution of this protein during development opens the question of its role in neural morphogenesis.     

Autoimmune target in Heymann nephritis is a glycoprotein with homology to the LDL receptor

The pathogenesis of Heymann nephritis, a rat model of human membranous glomerulonephritis, depends on the interaction of autoantibodies with a renal glycoprotein (GP330) on glomerular podocytes. Partial complementary DNAs coding for GP330 were isolated and sequenced. The deduced amino acid sequence from 4.3 kilobases of complementary DNA contains the sequences identical to two peptides derived from the isolated glycoprotein. The deduced amino acid sequence of this protein contains regions with homology to the human low density lipoprotein (LDL) receptor, an indication that GP330 and the LDL receptor may be members of the same gene family. Autoantibodies from the kidneys of rats with Heymann nephritis reacted with a nonglycosylated segment of GP330 that contains cysteine-rich 40-amino acid repeats, which are also features of the LDL receptor. GP330 is also similar in some regions to the mouse epidermal growth factor precursor.     

Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene

The HER-2/neu oncogene is a member of the erbB-like oncogene family, and is related to, but distinct from, the epidermal growth factor receptor. This gene has been shown to be amplified in human breast cancer cell lines. In the current study, alterations of the gene in 189 primary human breast cancers were investigated. HER-2/neu was found to be amplified from 2- to greater than 20-fold in 30% of the tumors. Correlation of gene amplification with several disease parameters was evaluated. Amplification of the HER-2/neu gene was a significant predictor of both overall survival and time to relapse in patients with breast cancer. It retained its significance even when adjustments were made for other known prognostic factors. Moreover, HER-2/neu amplification had greater prognostic value than most currently used prognostic factors, including hormonal-receptor status, in lymph node-positive disease. These data indicate that this gene may play a role in the biologic behavior and/or pathogenesis of human breast cancer.     

Structure of the GDP domain of EF-Tu and location of the amino acids homologous to ras oncogene proteins

A 2.7 angstrom resolution x-ray diffraction analysis of a trypsin-modified form of the Escherichia coli elongation factor Tu reveals that the GDP-binding domain has a structure similar to that of other nucleotide-binding proteins. The GDP ligand is located at the COOH-terminal end of the beta sheet and is linked to the protein via a Mg2+ ion salt bridge. The location of the guanine ring is unusual; the purine ring is located on the outer edge of the domain, not deep within a hydrophobic pocket. The amino acids from Pro10 to Arg44 and from Gly59 to Glu190 have been assigned to the electron density with computer graphic techniques, and the resulting model is consistent with all known biochemical data. An analysis of the structure reveals that four regions of the amino acid sequence that are homologous with the family of ras oncogene proteins, termed p21, are located in the vicinity of the GDP-binding site, and most of the invariant amino acids shared by the proteins interact directly with the GDP ligand.     

玉米抗矮花叶病基因的染色体定位及分子标记研究进展

综述了玉米抗矮花叶病基因染色体定位及分子标记的研究进展，并对RFLP，RAPD，SSR，AFLP等几种主要的分子标记在玉米遗传育种中的应用及发展前景作了初步探讨。     

Leucosulfakinin, a sulfated insect neuropeptide with homology to gastrin and cholecystokinin

A sulfated, myotropic neuropeptide termed leucosulfakinin (Glu-Gln-Phe-Glu-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-NH2) was isolated from head extracts of the cockroach Leucophaea maderae. The peptide exhibits sequence homology with the hormonally active portion of the vertebrate hormones human gastrin II and cholecystokinin, suggesting that these peptides are evolutionarily related. Six of the 11 amino acid residues (55 percent) are identical to those in gastrin II. In addition, the intestinal myotropic action of leucosulfakinin is analogous to that of gastrin.     

Genes for beta chain of human T-cell antigen receptor map to regions of chromosomal rearrangement in T cells

The T-cell antigen receptor is a cell-surface molecule that participates in the immune response. In the present experiments the genes encoding the beta chain of the T-cell receptor were found to reside on the long arm of human chromosome 7 at or near band q32. Related sequences were found on the short arm of chromosome 7 in bands p15-21 in some experiments. Chromosomal rearrangements in T-cells from normal individuals and patients with ataxia telangiectasia have previously been observed at and near these map assignments for the beta-chain genes.     

Human diabetes associated with a mutation in the tyrosine kinase domain of the insulin receptor

Insulin receptor complementary DNA has been cloned from an insulin-resistant individual whose receptors have impaired tyrosine protein kinase activity. One of this individual's alleles has a mutation in which valine is substituted for Gly996, the third glycine in the conserved Gly-X-Gly-X-X-Gly motif in the putative binding site fo adenosine triphosphate. Expression of the mutant receptor by transfection into Chinese hamster ovary cells confirmed that the mutation impairs tyrosine kinase activity.     

Human diabetes associated with a deletion of the tyrosine kinase domain of the insulin receptor

The insulin receptor has an intrinsic tyrosine kinase activity that is essential for signal transduction. A mutant insulin receptor gene lacking almost the entire kinase domain has been identified in an individual with type A insulin resistance and acanthosis nigricans. Insulin binding to the erythrocytes or cultured fibroblasts from this individual was normal. However receptor autophosphorylation and tyrosine kinase activity toward an exogenous substrate were reduced in partially purified insulin receptors from the proband's lymphocytes that had been transformed by Epstein-Barr virus. The insulin resistance associated with this mutated gene was inherited by the proband from her mother as an apparently autosomal dominant trait. Thus a deletion in one allele of the insulin receptor gene may be at least partly responsible for some instances of insulin-resistant diabetes.     

紫云英结瘤受体激酶靶蛋白的筛选与鉴定

利用酵母双杂交技术,以结瘤受体激酶(NORK)蛋白的跨膜结构域(TM)为诱饵,进行了与其相互作用靶蛋白的筛选鉴定.结果获得41个候选阳性克隆,通过测序和在NCBI中进行Blast比对分析,发现其中一个具有重要生物学功能的互作蛋白翻译延伸因子AsEF1-α,并将该蛋白相应的编码基因命名为AsEF1-α.进一步的验证表明靶蛋白AsEF1-α与诱饵互作的关键结构域是EF1-α-Ⅲ.     

Interaction of the IL-2 receptor with the src-family kinase p56lck: identification of novel intermolecular association

In the interleukin-2 (IL-2) system, intracellular signal transduction is triggered by the beta chain of the IL-2 receptor (IL-2R beta); however, the responsible signaling mechanism remains unidentified. Evidence for the formation of a stable complex of IL-2R beta and the lymphocyte-specific protein tyrosine kinase p56lck is presented. Specific association sites were identified in the tyrosine kinase catalytic domain of p56lck and in the cytoplasmic domain of IL-2R beta. As a result of interaction, IL-2R beta became phosphorylated in vitro by p56lck. Treatment of T lymphocytes with IL-2 promotes p56lck kinase activity. These data suggest the participation of p56lck as a critical signaling molecule downstream of IL-2R via a novel interaction.     

A calcium-dependent protein kinase with a regulatory domain similar to calmodulin.

Calcium can function as a second messenger through stimulation of calcium-dependent protein kinases. A protein kinase that requires calcium but not calmodulin or phospholipids for activity has been purified from soybean. The kinase itself binds calcium with high affinity. A complementary DNA clone for this kinase has been identified; it encodes a protein with a predicted molecular mass of 57,175 daltons. This protein contains a catalytic domain similar to that of calmodulin-dependent kinases and a calmodulin-like region with four calcium binding domains (EF hands). The predicted structure of this kinase explains its direct regulation via calcium binding and establishes it as a prototype for a new family of calcium-regulated protein kinases.