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 first description of an active form of a recombinant human T-cell leukemia virus type 1 (HTLV-1) reverse transcriptase (RT) and subsequent predictions of its amino acid sequence and quaternary structure are reported here. By using amino acid alignment methods, the NH2 and COOH termini of the RT, RNase H (RH), and integrase (IN) domains of the Pol polyprotein were determined. The HTLV-1 RT seems to be unique since its NH2 terminus is probably encoded by the pro open reading frame (ORF) fused downstream, via a transframe peptide, to the polypeptide encoded by the pol ORF. The HTLV-1 Pol amino acid sequence was revealed to be highly similar to that of Rous sarcoma virus (RSV), particularly at the RT-RH hinge region. These two domains remain linked for RSV; this may also be the case for HTLV-1. In light of these results, RT, RT-RH, and RT-RH-IN genes were constructed and introduced into His-tagged protein expression vectors. The corresponding proteins were synthesized in vitro, and the DNA polymerase activities of different protein combinations were tested. Solely the RT-RH-RT-RH-IN combination was found to have a significant activity level. Velocity sedimentation analysis suggested that the HTLV-1 RT-RH and RT-RH-IN monomers are likely associated in an oligomeric structure, probably of the alpha3/beta type.
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PMID:Human T-cell leukemia virus type 1 reverse transcriptase (RT) originates from the pro and pol open reading frames and requires the presence of RT-RNase H (RH) and RT-RH-integrase proteins for its activity. 965 93

The complete nucleotide sequence of the integrase (IN) protein coding region of the murine leukaemia virus (MLV) amphotropic strain 4070A is presented. The sequence comprises 1,224 nucleotides, encoding a 408-residue polypeptide of M(r) 46,312. Alignment of the inferred 4070A IN amino acid sequence with the IN proteins of other MLV showed that substitutions are confined largely to segments within the N- and C-terminal domains. In the N-terminal domain the majority of substitutions occur as contiguous 2- to 6-residue blocks, whereas in the C-terminal domain they occur as isolated entities except within a short segment characterized by deletions/insertions. Selection appears to act on the C-terminal 19 residues of IN rather than on the N-terminal residues of ENV (encoded by overlapping reading frames), suggesting a functional role for this segment. Phylogenetic analyses grouped the sequences into two clusters, one comprising IN from the amphotropic strain 4070A and three ecotropic MLV (CAS-BR-E, Moloney and Friend), the other consisting of IN from three ecotropic MLV (two radiation-induced viruses and AKV) and a mink cell focus-forming (MCF) MLV virus. The same dichotomy and cluster composition was obtained from analysis of the long terminal repeat (LTR) regions from these viruses (consistent with the functional interrelationship of IN and LTR) but not from analysis of envelope protein sequences (consistent with the functional independence of ENV proteins from both IN and LTR). Secondary structure predictions supported features determined from the catalytic domain of human immunodeficiency virus and avian sarcoma virus IN, and identified probable structures within the relatively long N- and C-terminal domains of MLV IN proteins.
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PMID:Nucleotide sequence of the murine leukaemia virus amphotropic strain 4070A integrase (IN) coding region and comparative structural analysis of the inferred polypeptide. 967 35

Retroviral DNA integration is mediated by the preintegration complex, a large nucleoprotein complex derived from the core of the infecting virion. We previously have used Mu-mediated PCR to probe the nucleoprotein organization of Moloney murine leukemia virus preintegration complexes. A region of protection spans several hundred base pairs at each end of the viral DNA, and strong enhancements are present near the termini. Here, we show that these footprints reflect a specific association between integrase and the viral DNA ends in functional preintegration complexes. Barrier-to-autointegration factor, a cellular protein that blocks autointegration of Moloney murine leukemia virus DNA, also plays an indirect role in generating the footprints at the ends of the viral DNA. We have exploited Mu-mediated PCR to examine the effect of mutations at the viral DNA termini on complex formation. We find that a replication competent mutant with a deletion at one end of the viral DNA still exhibits a strong enhancement about 20 bp from the terminus of the mutant DNA end. The site of the enhancement therefore appears to be at a fixed distance from the ends of the viral DNA. We also find that a mutation at one end of the viral DNA, which renders the virus incompetent for replication, abolishes the enhancements and protection at both the U3 and U5 ends. A pair of functional viral DNA ends therefore are required to interact before the chemical step of 3' end processing.
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PMID:Footprints on the viral DNA ends in moloney murine leukemia virus preintegration complexes reflect a specific association with integrase. 972 38

The C-terminal part of the pol gene of the human T-cell leukemia virus type I (HTLV-I) is predicted to encode the integrase (IN) of the virus; however, this protein has not yet been detected in virions or infected cells. We expressed the putative IN from an infectious molecular clone of HTLV-I in Escherichia coli. Comparison with protein resulting from coexpression of HTLV-I protease (PR) and Pol in insect cells indicated that the bacterially expressed protein is identical with or very similar to IN released from a PR-Pol precursor by proteolytic cleavage. HTLV-I IN was purified from E. coli under native conditions. The protein behaved like a dimer in size-exclusion chromatography. It carried out activities characteristic of retroviral IN with high efficiency, displaying a strong preference for U5-derived vs. U3-derived sequences in the processing and strand-transfer reactions. In the disintegration reaction, HTLV-I IN not only accepted the double-stranded branched substrate corresponding to the product of a strand-transfer reaction, but was also able to carry out a phosphoryl transfer on a branched molecule with a single-stranded or a single adenosine overhang.
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PMID:Characterization of human T-cell leukemia virus type I integrase expressed in Escherichia coli. 991 78

The retroviral integrase (IN) is required for the integration of viral DNA into the host genome. The N terminus of IN contains an HHCC zinc finger-like motif, which is conserved among all retroviruses. To study the function of the HHCC domain of Moloney murine leukemia virus IN, the first N-terminal 105 residues were expressed independently. This HHCC domain protein is found to complement a completely nonoverlapping construct lacking the HHCC domain for strand transfer, 3' processing and coordinated disintegration reactions, revealing trans interactions among IN domains. The HHCC domain protein binds zinc at a 1:1 ratio and changes its conformation upon binding to zinc. The presence of zinc within the HHCC domain stimulates selective integration processes. Zinc promotes the dimerization of the HHCC domain and protects it from N-ethylmaleimide modification. These studies dissect and define the requirement for the HHCC domain, the exact function of which remains unknown.
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PMID:Functional interactions of the HHCC domain of moloney murine leukemia virus integrase revealed by nonoverlapping complementation and zinc-dependent dimerization. 997 58

We compared the efficiency of transduction by an HIV-1-based lentiviral vector to that by a Moloney murine leukemia virus (MLV) retroviral vector, using stringent in vitro assays of primitive, quiescent human hematopoietic progenitor cells. Each construct contained the enhanced green fluorescent protein (GFP) as a reporter gene. The lentiviral vector, but not the MLV vector, expressed GFP in nondivided CD34(+) cells (45.5% GFP+) and in CD34(+)CD38(-) cells in G0 (12.4% GFP+), 48 hr after transduction. However, GFP could also be detected short-term in CD34(+) cells transduced with a lentiviral vector that contained a mutated integrase gene. The level of stable transduction from integrated vector was determined after extended long-term bone marrow culture. Both MLV vectors and lentiviral vectors efficiently transduced cytokine-stimulated CD34(+) cells. The MLV vector did not transduce more primitive, quiescent CD34(+)CD38(-) cells (n = 8). In contrast, stable transduction of CD34(+)CD38(-) cells by the lentiviral vector was seen for over 15 weeks of extended long-term culture (9.2 +/- 5.2%, n = 7). GFP expression in clones from single CD34(+)CD38(-) cells confirmed efficient, stable lentiviral transduction in 29% of early and late-proliferating cells. In the absence of growth factors during transduction, only the lentiviral vector was able to transduce CD34(+) and CD34(+)CD38(-) cells (13.5 +/- 2.5%, n = 11 and 12.2 +/- 9.7%, n = 4, respectively). The lentiviral vector is clearly superior to the MLV vector for transduction of quiescent, primitive human hematopoietic progenitor cells and may provide therapeutically useful levels of gene transfer into human hematopoietic stem cells.
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PMID:Stable transduction of quiescent CD34(+)CD38(-) human hematopoietic cells by HIV-1-based lentiviral vectors. 1007 24

To examine the early events in the life cycle of Moloney murine leukemia virus (MoMLV), we analyzed the intracellular complexes mediating reverse transcription. Partial purification of the reverse transcription complexes (RTCs) by equilibrium density fractionation and velocity sedimentation indicated that three distinct species of intracellular complexes are formed shortly after cell infection. Only one of these species is able to start and complete reverse transcription in the cell cytoplasm. This RTC is composed of at least the viral genome, capsid, integrase, and reverse transcriptase proteins. The RTC becomes permeable to micrococcal nuclease but not to antibodies. Shortly after initiation of reverse transcription, the viral strong stop DNA within the RTC is protected from nuclease digestion. The sedimentation velocity of the RTC decreases during reverse transcription. After entry into the nucleus, most capsid proteins are lost from the RTC and its sedimentation velocity decreases further.
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PMID:Characterization of intracellular reverse transcription complexes of Moloney murine leukemia virus. 1051 96

We report the complete nucleotide sequence of the potent T-lymphomagenic murine retrovirus SL3-3. The non-LTR regions of the virus show 98% sequence identity to the endogenous ecotropic Akv murine leukemia virus. While the region encoding the surface envelope protein is completely identical to that of Akv, a approximately 200 nucleotide stretch in the integrase encoding region upstream of env is similar to the sequence of mink cell focus forming (MCF) viruses and shows a complete match with the mouse retrovirus 10A1. The history of SL3-3 may therefore include recombination involving an Akv-like virus and a virus with MCF-like sequences.
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PMID:The nucleotide sequence of the high-leukemogenic murine retrovirus SL3-3 reveals a patch of mink cell focus forming-like sequences upstream of the ecotropic envelope gene. Brief report. 1060 74

A replication-deficient recombinant adenovirus encoding luciferase was constructed using 5' and 3' long terminal repeat (LTR) sequences of the Moloney murine leukemia virus. Gene expression was observed in cultured cells in vitro and in submandibular gland, cortex, and caudate nucleus for as long as three months in vivo. The vector integrated randomly into the genome of both dividing and nondividing cells as determined by fluorescence in situ hybridization (FISH) (10-15% of cells in vitro and 5% in rat spleen in vivo), gene walking, Southern hybridization, and polymerase chain reaction (PCR), in the absence of transcomplementing reverse transcriptase or integrase activity. The new vector combines the high titer and versatility of adenoviral vectors with the long-term gene expression and integration of retroviral vectors.
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PMID:Genomic integration and gene expression by a modified adenoviral vector. 1065 18

Concerted integration of retrovirus DNA termini into the host chromosome in vivo requires specific interactions between the cis-acting attachment (att) sites at the viral termini and the viral integrase (IN) in trans. In this study, reconstruction experiments with purified avian myeloblastosis virus (AMV) IN and retrovirus-like donor substrates containing wild-type and mutant termini were performed to map the internal att DNA sequence requirements for concerted integration, here termed full-site integration. The avian retrovirus mutations were modeled after internal att site mutations studied at the in vivo level with human immunodeficiency virus type 1 (HIV-1) and murine leukemia virus (MLV). Systematic overlapping 4-bp deletions starting at nucleotide positions 7, 8, and 9 in the U3 terminus had a decreasing detrimental gradient effect on full-site integration, while more internal 4-bp deletions had little or no effect. This decreasing detrimental gradient effect was measured by the ability of mutant U3 ends to interact with wild-type U3 ends for full-site integration in trans. Modification of the highly conserved C at position 7 on the catalytic strand to either A or T resulted in the same severe decrease in full-site integration as the 4-bp deletion starting at this position. These studies suggest that nucleotide position 7 is crucial for interactions near the active site of IN for integration activity and for communication in trans between ends bound by IN for full-site integration. The ability of AMV IN to interact with internal att sequences to mediate full-site integration in vitro is similar to the internal att site requirements observed with MLV and HIV-1 in vivo and with their preintegration complexes in vitro.
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PMID:Avian retrovirus DNA internal attachment site requirements for full-site integration in vitro. 1095 27


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