Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumor necrosis factor (TNF) is a soluble protein that causes damage to tumor cells but has no effect on normal cells. Human TNF was purified to apparent homogeneity as a 17.3-kilodalton protein from HL-60 leukemia cells and showed cytotoxic and cytostatic activities against various human tumor cell lines. The amino acid sequence was determined for the amino terminal end of the purified protein, and oligodeoxyribonucleotide probes were synthesized on the basis of this sequence. Complementary DNA (cDNA) encoding human TNF was cloned from induced HL-60 messenger RNA and was confirmed by hybrid-selection assay, direct expression in COS-7 cells, and nucleotide sequence analysis. The human TNF cDNA is 1585 base pairs in length and encodes a protein of 233 amino acids. The mature protein begins at residue 77, leaving a long leader sequence of 76 amino acids. Expression of high levels of human TNF in Escherichia coli was accomplished under control of the bacteriophage lambda PL promoter and gene N ribosome binding site.
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PMID:Molecular cloning of the complementary DNA for human tumor necrosis factor. 385 24

The K562 human leukemia cell is an erythroid-like cell that may serve as a model for the study of globin gene expression in transcriptionally active human erythroid cells. K562 cells express all globin genes with the exception of that for beta-globin; failure to produce beta-globin could result from an acquired mutation in each of the beta-globin genes or from an alteration in the regulatory factor environment of the beta-globin gene. To uncover a possible acquired mutation, restriction endonuclease analysis of genomic K562 DNA and expression studies of a cloned K562 beta-globin gene were carried out. Restriction endonuclease analysis revealed no structural alteration of the K562 beta-globin genes. Analysis of the polymorphic Ava II site in intervening sequence 2 of the beta-globin gene showed that K562 cells contain two different beta-globin alleles, both of which are inactive. A K562 beta-globin gene was cloned, ligated into the expression vector pLTN3B, and introduced into COS cells. Transcripts were analyzed by RNA blot, dot blot, S1 nuclease mapping, and primer extension assay. The cloned K562 beta-globin gene was transcribed in COS cells as efficiently as a normal beta-globin gene introduced into COS cells; the mRNA was 10 S and polyadenylylated; the 5' and 3' termini and the processing of transcripts were identical to that of mRNA transcribed from a normal gene. Based on these data we suggest that the absence of beta-globin gene expression results not from an alteration in the beta-globin gene, but from a quantitative or qualitative alteration in a trans-acting factor important in beta-globin gene expression.
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PMID:A beta-globin gene, inactive in the K562 leukemic cell, functions normally in a heterologous expression system. 620 98

The integrin receptor alpha 4 beta 1 binds to two different ligands, the extracellular matrix glycoprotein fibronectin and the endothelial cell surface protein vascular cell adhesion molecule-1 (VCAM-1). Using probes derived from each ligand and a variety of cell adhesion and ligand-receptor binding assays, we have investigated the relationship between the mechanisms of fibronectin and VCAM-1 interaction with alpha 4 beta 1. CS1 peptide, which represents the dominant active site from the HepII/IIICS recognition domain in fibronectin, was found to inhibit VCAM-1-dependent adhesion in three different assays: MOLT-4 T lymphoblastic leukaemia cell attachment to immobilized recombinant soluble VCAM-1 (rsVCAM-1), MOLT-4 cell attachment to monolayers of VCAM-1-transfected COS-1 cells, and A375-SM melanoma cell spreading on immobilized rs VCAM-1. Half-maximal inhibition required CS1 concentrations of 1.7-3.0 mg/ml, some 3-7-fold higher than that needed to autoinhibit adhesion to CS1-IgG conjugate. Using a more sensitive solid-phase receptor-ligand binding assay, CS1 was found to be a potent inhibitor of the binding of rsVCAM-1 to alpha 4 beta 1 (half-maximal inhibition at 13 micrograms/ml). In agreement with cell-based assays, severalfold lower concentrations of CS1 were required to inhibit binding of recombinant HepII/IIICS region of fibronectin (half-maximal inhibition at 3 micrograms/ml). VCAM-1-alpha 4 beta 1 binding was blocked not only by CS1 peptide but also by the recombinant HepII/IIICS region of fibronectin. Kinetic analysis of CS1 inhibition of VCAM-1 binding revealed that it was directly competitive in nature, indicating that VCAM-1 and fibronectin recognize either identical or spatially overlapping binding sites on alpha 4 beta 1. The implications of these results for the future design of VCAM-1 antagonists are discussed.
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PMID:Competitive binding of vascular cell adhesion molecule-1 and the HepII/IIICS domain of fibronectin to the integrin alpha 4 beta 1. 750 37

The chimeric BCR/ABL protein is characteristic of Philadelphia (Ph)+ leukemia because it is the direct product of the Ph translocation and it has been shown to play a causal role in the genesis of leukemia. The BCR/ABL protein exhibits a deregulated tyrosine-kinase activity capable of phosphorylating different cellular substrates in vivo and in vitro. CRKL, an adaptor protein consisting of SH2 and SH3 domains in the absence of a catalytic domain, is one potential in vivo substrate of BCR/ABL. Previous experiments have shown that CRKL is phosphorylated on tyrosine in the chronic myelogenous leukemia (CML) cell line K562 and that CRKL is a substrate for ABL and for BCR/ABL in COS-1 cells. In the current study, we show that in peripheral blood cells a direct correlation exists between the presence of BCR/ABL and the phosphorylation status of CRKL. In Ph- peripheral blood cells, CRKL is present only in the nonphosphorylated form. In contrast, all BCR/ABL+ CML and acute lymphoblastic leukemia patient samples examined showed clear tyrosine-phosphorylation of CRKL. This result strongly suggests that CRKL is a biologically significant substrate for BCR/ABL and is likely to play a major role in the development of Ph+ leukemia.
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PMID:Tyrosine phosphorylation of CRKL in Philadelphia+ leukemia. 752 85

In previous in vitro studies we found that contact between mouse primordial germ cells and other cell types (neighbouring somatic cells or established TM4 or STO cell lines) is crucial for supporting primordial germ cell survival and proliferation and for activating their motility. We have studied primordial germ cell adhesion to different cell monolayers (STO, TM4, COS and F9 cells) as an in vitro model for interactions between primordial germ cells and cellular substrates. The results suggest that these cell interactions are mediated by multiple mechanisms involving Steel factor and its receptor encoded by c-kit, carbohydrates and possibly other unknown factors. We find that Steel factor and leukaemia inhibitory factor are survival rather than proliferation factors for primordial germ cells. Both molecules prevent primordial germ cell death in culture by suppressing apoptosis. Morphological and molecular features of primordial germ cell apoptosis in vitro are reported. Activation of protein kinase C does not promote primordial germ cell proliferation, but compounds known to enhance intracellular levels of cAMP (i.e. dibutyryl cAMP and forskolin) markedly stimulate primordial germ cells to proliferate in culture. We have preliminary results indicating that neuropeptides PACAP-27 and PACAP-28 are possible physiological activators of adenylate cyclase in primordial germ cells.
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PMID:Interactions between migratory primordial germ cells and cellular substrates in the mouse. 753 Jun 18

Moloney murine leukemia virus (Mo-MuLV) genomic mRNA codes for two gag precursors by alternative initiations of translation. An AUG codon governs the synthesis of the retroviral capsid proteins precursor, whereas a CUG codon directs the synthesis of a glycosylated cell surface antigen, the gross cell surface antigen. Control of the relative synthesis of the two precursors is crucial for MuLV infectivity and pathology. Furthermore, the MuLV mRNA leader sequence is very long and should inhibit translation according to the classical scanning model. This suggests a different translation initiation mechanism allowing gag efficient expression. We demonstrate, by using bicistronic vectors expressed in COS-7 cells, that the Mo-MuLV mRNA leader drives translation initiation by internal ribosome entry. We have localized the internal ribosome entry site (IRES) between the two initiation codons. This 126 nucleotide long IRES implies an oligopyrimidine tract located 45 nucleotides upstream of AUG codon. UV cross-linking and affinity chromatography experiments show that the PTB/p57 splicing factor specifically interacts with this oligopyrimidine tract. The MuLV IRES controls alternative translation initiation by activating the capsid protein precursor expression. This gag translational enhancer could exist in other retroviruses.
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PMID:Alternative translation initiation of the Moloney murine leukemia virus mRNA controlled by internal ribosome entry involving the p57/PTB splicing factor. 765 11

Clustering of beta 1-integrins on adherent cells with antibodies or ligands results in increased tyrosine phosphorylation and activation of a novel focal adhesion tyrosine kinase, pp125FAK. The genes encoding pp125FAK have been cloned previously from both chicken and mouse cDNA libraries, and the deduced amino acid sequences are nearly identical (94%). Two synthetic peptides derived from sequences at the carboxyl terminus of chicken pp125FAK were conjugated to ovalbumin to generate rabbit heteroantisera. Human pp125FAK was immunodetected in both T and B lymphocytes with these antisera. A basal state of pp125FAK tyrosine phosphorylation was observed in T and B lymphocytes, and its expression level was in general augmented among human T- and B-cell leukemia/lymphoma lines. Additionally, the full-length sequence of human T-cell pp125FAK (huT-FAK) was derived from a Jurkat T-cell cDNA library. huT-FAK is structurally identical with both mouse and chicken FAK, and shares 95% amino acid identity with chicken pp125FAK and has 97% homology with the mouse sequence. This high degree of evolutionary conservation between species suggests that pp125FAK is likely to have a crucial function in the cell. Expression of the full-length huT-FAK gene in COS cells showed an immunologically indistinct human pp125FAK protein compared with the endogenous primate pp125FAK. Taken together, the data indicate that this structurally conserved human T-cell pp125FAK likely functions in T- and B-cell lineages, and its altered expression in human lymphocyte tumor cell lines may contribute to their transformed phenotype.
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PMID:Human T and B lymphocytes express a structurally conserved focal adhesion kinase, pp125FAK. 769 78

We determined the nucleotide sequence of a 2.6-kb BamHI-EcoRI fragment from the 5'-end of the human gene encoding the cell adhesion receptor, CD36. This region contains the first coding exon, exon 3, as well as two non-coding exons, exons 2a and 2b, from the 5'-flanking region. Also present in the 5'-flanking region are two Alu repeats belonging to the Alu-Sa subfamily. When the determined genomic sequence was compared to a placental cDNA sequence [Oquendo et al., Cell 58 (1989) 95-101] and to a human erythroid leukemia (HEL) cell CD36 cDNA sequence (this report), we found that exons 2a and 2b do not occur within the same mRNA, suggesting that alternative splicing occurs within the 5'-untranslated region (UTR) of human CD36 pre-mRNA. These observations were confirmed by reverse transcriptase-coupled polymerase chain reaction (RT/PCR) assays using RNA from placental tissue, HEL cells and human platelets. Exon 2b encodes two alternative translation initiation codons which may render exon 2b-containing CD36 mRNA untranslatable. To test this hypothesis, we transfected COS-1 cells with an exon 2b-containing CD36 cDNA construct. Using anti-CD36 polyclonal antibody, we were able to detect an immunoreactive protein, consistent in size with the mature protein observed in transfected COS-1 cells. Therefore, exon 2b itself is insufficient to block translation of CD36 mRNA.
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PMID:Characterization of two alternatively spliced 5'-untranslated exons of the human CD36 gene in different cell types. 769 52

We developed a novel method for analysis of hepatitis C viral proteinase activity in cultured cells, in which the proteinase activity was measured as the enhancement of reporter gene expression. In this system, plasmids encoding a reporter gene, the enzyme gene, and the substrate gene were simultaneously transfected into COS-1 cells. The reporter plasmid contains chloramphenicol acetyltransferase (CAT) gene downstream of an enhancer/promoter sequence derived from the human T-cell leukemia virus type-1 (HTLV-I) long-terminal repeat (LTR). The substrate expression plasmid was a triple chimera; HCV nonstructural protein 2 (NS2) and the Tax1 protein of HTLV-I sandwiched the substrate polypeptide, which was inserted upstream of Tax1. This method assumes that since the HCV NS2 appears to be located in the lipid bilayer of endoplasmic reticulum (ER) membranes, the Tax1 of the chimeric substrate was trapped on the surface of the ER in the absence of HCV proteinase activity. After release from the chimera by HCV proteinase-dependent cleavage, Tax1 could transactivate the expression of the CAT gene through the enhancer sequence of HTLV-I LTR. This system should enable us to simply and safely screen the potential antiviral activity of proteinase inhibitors in vivo, although this system may be limited to proteinase inhibitors that are permeable to the plasma membrane.
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PMID:A novel method for analysis of viral proteinase activity encoded by hepatitis C virus in cultured cells. 777 61

A cDNA encoding a human IL-12R subunit was isolated by expression cloning. This subunit is a 662 amino acid type I transmembrane protein with an extracellular domain of 516 amino acids and a cytoplasmic domain of 91 amino acids. It is a member of the hemopoietin receptor superfamily and is most closely related over its entire length to gp130 and the receptors for granulocyte-CSF (G-CSF) and leukemia-inhibitory factor. When expressed in COS cells, this IL-12R subunit binds both human and murine IL-12 with an apparent affinity of 2 to 5 nM. The transfected COS cells express both monomers and disulfide-linked dimers or oligomers of the IL-12R subunit on their surface. However, unlike the IL-6-induced dimerization of gp130, the oligomerization of the IL-12R subunit is not dependent on binding of IL-12. Only the IL-12R subunit dimers/oligomers but not the monomers bind IL-12 with an affinity of 2 to 5 nM. A polyclonal antiserum raised against this receptor subunit specifically inhibits IL-12-induced proliferation of PHA-activated PBMC. The data are consistent with the hypotheses that 1) a dimer/oligomer of the cloned IL-12R subunit (IL-12R-beta) represents the low affinity IL-12 binding site identified on human lymphoblasts, 2) the cloned receptor subunit is involved in IL-12 signal transduction, and 3) an additional, as of yet unidentified subunit is required to generate a high affinity IL-12R complex.
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PMID:Expression cloning of a human IL-12 receptor component. A new member of the cytokine receptor superfamily with strong homology to gp130. 791 93


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