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)

The ATF/CRE binding site can mediate transcriptional activation by cAMP, the adenovirus E1A protein and the human T-cell leukaemia virus 1 (HTLV1) tax protein. A large number of different proteins bind specifically to this element either as homodimers or as heterodimers. Using GAL4-ATF/CREB fusions, we have investigated the regulatory functions of three members of this family. CREB1 (CREB) is strongly activated by cAMP and weakly activated by the E1A protein. In contrast, CREB2 (CRE-BP1, ATF2) is strongly activated by E1A but is insensitive to cAMP stimulation. ATF1 is weakly activated by cAMP but is not activated by E1A. All three proteins are insensitive to activation by the HTLV1 tax protein. The N-terminal region of CREB2, from amino acid residues 19 to 112, is both necessary and sufficient for E1A activation. This region contains a putative C2H2 metal-binding finger, and single amino acid substitutions of the cysteine residues severely decreased CREB2 activity. In contrast, mutations affecting a potential protein kinase A and casein kinase II phosphorylation site within this region had little effect.
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PMID:Differential regulation of three members of the ATF/CREB family of DNA-binding proteins. 165 8

The binding of haemopoietic growth factors and cytokines to specific receptors triggers a cascade of intracellular events which results in cell proliferation and differentiation. The knowledge of ligand-receptor-signal pathways is not only important in understanding the pathophysiology of malignant disease but also essential for devising future therapeutic strategies. The advent of recombinant technology has made it possible to test the efficacy of selective differentiation therapy, and haemopoietic growth factors are undergoing clinical trials for a number of indications. In addition, increasingly the receptors for haemopoietic growth factors and cytokines have come under scientific scrutiny. Recently receptors for IL-2 alpha, IL-2 beta, IL-3, IL-4, IL-5, IL-6, IL-7, erythropoietin, G-CSF and GM-CSF have been isolated and cloned. It has become apparent that they have structural homology that is shared by receptors for growth hormone and prolactin, and this receptor group makes up the new cytokine receptor superfamily. The finding of sequence homology within these receptors suggests their evolutionary relationship. These receptors are transmembrane proteins 257-856 amino acids and their extracellular ligand-binding domain contains four conserved cysteine residues and a Trp-Ser-X-Trp-Ser motif. The secondary structure of the extracellular domain is made up of alpha-helices. High and low affinity binding forms exist for all these receptors. Binding affinity may depend on the formation of receptor heterodimers or multimers, association with other membrane proteins or differential glycosylation. Soluble receptor forms have been described for IL-2 alpha, IL-4, IL-5, IL-6 and IL-7. It is not known whether they are actively secreted or represent the degradation products of cell turnover. Their function may be to mop up excess cytokines and thereby confine the cytokine response. There is no sequence homology of the intracytoplasmic domains although several are rich in proline and serine residues, which may be important in mechanisms of signal transduction. No receptor in this superfamily functions as a receptor tyrosine kinase or has intrinsic protein tyrosine kinase activity. Detailed study of individual receptors holds clues to the regulation of receptor expression, ligand-receptor interactions and mechanisms involved in signal transduction. Such knowledge might explain the pleotropic effects cytokines may have on different cell types and their overlap in biological functions. Elevated levels of soluble IL-2 alpha receptor (Tac) are detected in hairy cell leukaemia, lymphomas and adult T-cell leukaemia (TL), and levels reflect tumour burden.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The cytokine receptor superfamily. 166 10

The core of retroviruses contains a highly conserved, low molecular weight, basic protein that binds nucleic acids and is essential for genomic RNA packaging. The 56 amino acid protein, NCp10, of Moloney Murine Leukaemia virus (MoMuLV) has the CysX2 CysX4 HisX4 Cys zinc finger-like motif shared by all retrovirus nucleocapsid proteins. The native protein and five modified peptides containing the zinc binding domain were synthesized by solid phase in order to investigate the structural and biochemical role of Zn2+ chelation in MoMuLV NCp10 activity. The purity of the synthetic molecules was verified by HPLC and their sequences were confirmed by amino acid analysis and sequencing in the case of NCp10. Thiol dosage agreed with the theoretical value of free cysteine for all these molecules. Fluorescence measurements performed on synthetic NCp10 and zinc finger fragments showed that the tryptophan quantum yield was Zn2(+)-dependent, allowing a 1:1 stoichiometry for the complex to be determined. The apparent affinity constant of NCp10 for the metal was estimated to be superior to 10(6) M-1. The synthetic protein, in the presence of Zn2+ ions, possesses all the biological properties of NCp10 isolated from virions. It catalyzes both the MoMuLV RNA dimerization and the annealing of the replication primer tRNA(Pro) onto MoMuLV RNA.
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PMID:Solid phase synthesis of the retroviral nucleocapsid protein NCp10 of Moloney murine leukaemia virus and related "zinc-fingers" in free SH forms. Influence of zinc chelation on structural and biochemical properties. 170 45

Envelope glycoprotein 71 from Friend murine leukemia virus was purified to homogeneity by reversed-phase HPLC. It could be shown that all 20 cysteine residues of the molecule are linked by disulfide bonds. After complete tryptic digestion, peptides containing cystine were identified by comparison of the reversed-phase HPLC profile of the digest with that of a reduced aliquot which had been subjected to affinity chromatography on thiol-Sepharose. The locations of the 10 disulfide bonds were determined by isolation, further digestion and analysis of peptides containing cystine. The first cysteine residue of the sequence (Cys46) was shown to be coupled to the sixth (Cys98), leading to a large loop containing four additional cysteine residues. Computer model building and energy calculations led to the assignment of Cys72 to Cys87 and Cys73 to Cys83. The following four cysteine residues of the sequence also constitute a structural unit, with Cys121 bonded to Cys141 and Cys133 to Cys146, and the last two cysteine residues in the amino-terminal domain of glycoprotein 71 form a small loop (Cys178 to Cys184). The first two cysteine residues of the carboxy-terminal domain produce a very small hydrophobic loop (Cys312-Cys315). Cys361 is bound to Cys373, Cys342 to Cys396 and Cys403 to Cys416. A model for the folding pattern of the viral glycoprotein is proposed.
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PMID:Localization of the intrachain disulfide bonds of the envelope glycoprotein 71 from Friend murine leukemia virus. 173 Feb 42

The p53 gene was examined in primary lymphoblasts of 25 pediatric patients with acute lymphoblastic leukemia by the RNase protection assay and by single strand conformation polymorphism analysis in 23 of 25 cases. p53 mutations were found to occur, but at a low frequency (4 of 25). While all four mutations were identified by single strand conformation polymorphism, the comparative sensitivity of RNase protection was 50% (2 of 4). Heterozygosity was retained at mutated codons in 3 of 4 cases. One pedigree was consistent with the Li-Fraumeni syndrome, and bone marrow from both diagnosis and remission indicated a germline G to T transversion at codon 272 (valine to leucine). Although members of another family were affected with leukemia, a 2-bp deletion in exon 6 was nonhereditary. The other two nonhereditary p53 mutations included a T to G transversion at codon 270 (phenylalanine to cysteine) and a G to C transversion at codon 248 (arginine to proline). These data support the role of both hereditary and acquired p53 mutations in the pathogenesis and/or progression of some cases of childhood acute lymphoblastic leukemia.
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PMID:Hereditary and acquired p53 gene mutations in childhood acute lymphoblastic leukemia. 173 52

The mitogenic membrane glycoprotein (gp55) encoded by Friend erythroleukemia virus is inefficiently processed from the rough endoplasmic reticulum (RER) and only 3-5% reaches plasma membranes. Because this processed component (gp55P) contains larger and more complex oligosaccharides, it can be separated from RER gp55. In nonreducing conditions, gp55P is a unique disulfide-bonded dimer, whereas RER gp55 consists of monomers and dimers with diverse intrachain and interchain disulfide bonds. This suggests that gp55 folds heterogeneously and that only one homodimer is competent for export from the RER. Pulse-chase analyses of gp55 components labeled with radioactive amino acids indicated that formation of diverse disulfide-bonded components occurred within minutes of polypeptide synthesis and that malfolded components did not later isomerize to generate dimers competent for export from the RER. Chemical studies suggested that all 12 cysteines of gp55 were oxidized within 5 min after synthesis of the protein. In contrast, the envelope glycoprotein precursor (gPr90) encoded by a replication-competent murine leukemia virus folds more homogeneously, and it is then processed and cleaved to form an extracellular glycoprotein gp70 plus a transmembrane protein p15E. The fully processed glycoprotein contains an unoxidized cysteine sulfhydryl that isomerizes reversibly with a disulfide bond that links gp70 to p15E. Consequently, only a proportion of gp70 and p15E is disulfide-bonded, and dissociation occurs when the environment becomes even slightly reducing. The gp55 glycoprotein appears to be an extreme example of protein malfolding associated with imprecise and irreversible disulfide bonding. We discuss evidence that folding inefficiencies are common for retroviral proteins that have newly evolving pathogenic functions.
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PMID:Disulfide bonding controls the processing of retroviral envelope glycoproteins. 174 94

Abnormalities of p53 mRNA in adult T-cell leukemia (ATL) were analyzed using reverse transcription-polymerase chain reaction-single strand conformation polymorphism analysis. Mutations were present in two of 12 ATL patients studied, but not in 3 cell lines immortalized by human T cell leukemia virus type 1 (HTLV-1) infection in vitro. Direct sequencing analysis of the p53 gene from these two patients revealed missense point mutations at codon 153 (arginine to histidine) or codon 220 (cysteine to tyrosine), respectively. Immunohistochemical analysis revealed the elevated expression of p53 proteins in ATL cells from a patient carrying the mutated p53 gene at codon 158. Neither gross rearrangement of p53 gene nor abnormal size of mRNA for the gene was demonstrated by Southern or Northern blot analyses. Thus, there is a mutated p53 in some patients with ATL. The involvement of abnormalities in some suppressor oncogenes may play a role in the development of ATL.
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PMID:Genetic alteration of p53 in some patients with adult T-cell leukemia. 177 65

The presence of activated transforming genes was investigated in four patients with therapy-related leukemia and in three with therapy-related myelodysplastic syndrome. DNA of bone marrow cells from six of the patients exhibited transforming activity in the tumorigenicity assay. Five of the six patients who were positive in the tumorigenicity assay contained activated N-ras oncogenes, and three contained activated K-ras oncogenes. Thus, concurrent activation of N-ras and K-ras oncogenes was observed in two patients. In vitro DNA amplification followed by oligonucleotide dot-blot analysis was used to investigate mutations in codons 12, 13, and 61 of the N-ras and K-ras oncogenes. Two patients exhibited an N-ras mutation, substituting aspartic acid (GAT) for glycine (GGT), and three patients exhibited an N-ras codon 13 mutation, substituting valine (GTT) for glycine. Two patients exhibited K-ras codon 12 mutations, substituting aspartic acid (GAT) or cysteine (TGT) for glycine (GGT), respectively, and one case exhibited a K-ras codon 61 mutation, substituting lysine (AAA) for glutamic acid (CAA). Cytogenetic analysis revealed that loss of chromosome 7 was frequent (four patients: 57%). Our data indicate that activation of N-ras and K-ras genes, as well as loss of heterozygosity for specific alleles on chromosome 7, plays a more important role in the leukemogenesis of both therapy-related leukemia and myelodysplastic syndrome.
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PMID:Transforming genes and chromosome aberrations in therapy-related leukemia and myelodysplastic syndrome. 185 83

2(R,S)-D-ribo-(1',2',3',4'-Tetrahydroxybutyl)-thiazolidine-4(R)-ca rboxylic acid (RibCys) is a prodrug of L-cysteine that releases the sulfhydryl amino acid after nonenzymatic ring opening and hydrolysis. The L-cysteine then elevates glutathione (GSH) levels by stimulating its biosynthesis. RibCys was investigated for its ability to protect CDF1 mice from the potent urotoxicity of cyclophosphamide (CTX) without compromising the therapeutic utility of the drug. RibCys induced a significant reduction in weight loss of the animals and in bladder inflammation at 48 h after CTX administration; however, bladder tissue remained inflamed as compared with that in controls. Bladder histology also showed some pathological changes in the presence of RibCys. In contrast, all parameters of toxicity (body weight loss, bladder inflammation, and pathological abnormalities) had been virtually reversed by day 21 after administration. In tests against L1210 leukemia, RibCys did not interfere with CTX anticancer activity. From these preliminary studies, RibCys appears to be a likely candidate for protecting against long-term CTX toxicity, perhaps reversing the original damage caused by a very high dose, without compromising the therapeutic utility of the alkylating agent.
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PMID:L-cysteine prodrug protects against cyclophosphamide urotoxicity without compromising therapeutic activity. 185 73

The complementary DNA sequence encoding the cell-surface receptor for ecotropic host-range murine retroviruses (ecoR) shows that it contains 622 amino acids and 14 hydrophobic potentially membrane-spanning sequences. Because this receptor occurs on many or all murine cells and is probably essential for viability of cultured fibroblasts, its normal function might be to transport an essential metabolite. We expressed ecoR in Xenopus laevis oocytes by injecting RNA transcribed from the cloned cDNA. These oocytes specifically bound the gp70 envelope glycoprotein from an ecotropic murine leukaemia virus. An inward current was recorded electrophysiologically when a mixture of amino-acids was applied: this resulted from a stereoselective, saturable uptake of lysine, arginine and ornithine; it was independent of sodium and not substantially altered by gp70. Cysteine and homoserine were also taken up, but sodium was necessary for their transport. These properties of ecoR correspond to those of the y+ amino-acid transporter. Our results demonstrate the subversion of a ubiquitous cell membrane protein, in this case a basic amino acid transporter, for use as a retroviral receptor.
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PMID:Cell-surface receptor for ecotropic murine retroviruses is a basic amino-acid transporter. 187 78


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