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

The protein-DNA and protein-protein interactions important for function of the integrase (IN) protein of Moloney murine leukemia virus (M-MuLV) were investigated by using a coordinated-disintegration assay. A panel of M-MuLV IN mutants and substrate alterations highlighted distinctions between the intermolecular and intramolecular reactions of coordinated disintegration. Mispairing of the crossbone single-strand region and altered long terminal repeat (LTR) positioning affected the intermolecular, but not the intramolecular, reactions of coordinated disintegration. Partial components of the crossbone substrate were coordinated by M-MuLV IN, indicating a reliance on both LTR and target DNA determinants for substrate assembly. The intramolecular reaction was dependent on the presence of either the HHCC domain or a crossbone LTR 5' single-stranded tail. An M-MuLV IN mutant without the HHCC domain (Ndelta105) catalyzed reduced levels of double disintegration but not single disintegration. A separately purified HHCC domain protein (Cdelta232) stimulated double disintegration mediated by Ndelta105, suggesting a role of the N-terminal HHCC domain in stable IN-IN and IN-DNA interactions. Significantly, crossbone substrates lacking the LTR 5' tails were not recognized by the fingerless Ndelta105 protein. Collectively, these data suggest similar roles of the HHCC domain and 5' LTR tail in substrate recognition and modulation of IN activity.
 ...
PMID:Coordinated disintegration reactions mediated by Moloney murine leukemia virus integrase. 864 28

The human immunodeficiency virus type 1 (HIV-1) Vif protein is necessary at the time of viral particle formation yet functionally manifests its effect after virions enter target cells. This suggests that Vif either acts on another viral protein or is itself incorporated into particles. In this study, we have examined the latter possibility. We confirm our previous observation that Vif is incorporated into human immunodeficiency virus type 1 virions at a ratio of approximately 1 molecule of Vif for every 75 to 220 molecules of p24, or 7 to 20 molecules per virion. Furthermore, we demonstrate that the relative concentration of Vif is much lower in particles than in infected cells, whereas the opposite is observed for the main virus components. The viral envelope, Nef, Vpr, Vpu, protease, reverse transcriptase, integrase, nucleocapsid, and p6gag proteins as well as the viral genomic RNA are dispensable for Vif packaging. Furthermore, mutating several highly conserved residues (H-108, C-114, C-133, L-145, and Q-146) or deleting the C-terminal 18 amino acids of Vif, either of which severely impairs Vif function, does not abolish its incorporation into virions. Finally, Vif can be packaged into murine leukemia virus particles. On the basis of these data, we conclude that the specificity of Vif incorporation into virions remains an open question.
 ...
PMID:Characterization of human immunodeficiency virus type 1 Vif particle incorporation. 870 34

Foamy or spumaviruses are complex retroviruses. Phylogenetic trees have been constructed previously for either the polymerase or integrase domains showed a clustering of the foamy viruses relatively distant from other retroviruses. The most related retrovirus was found to be murine leukemia virus, irrespective of the method used or foamy viral gene analyzed. We analyze bel genes of different foamy viruses and compared the corresponding phylogenetic trees with those obtained from the pol genes that were constructed with refined computer programs. In addition, the nucleocapsid protein sequence of foamy viruses was used for a comparative phylogenetic analysis. Known biological properties of the individual FV protein domains are discussed to ascertain the apparent phylogenetic relatedness.
 ...
PMID:Analysis of the phylogenetic placement of different spumaretroviral genes reveals complex pattern of foamy virus evolution. 882 44

The long terminal repeats (LTRs) that flank the retroviral DNA genome play a distinct role in the integration process by acting as specific substrates for the integrase (IN). The role of LTR sequences in providing substrate recognition and specificity to integration reactions was investigated for INs from human immunodeficiency virus type 1 (HIV-1), Moloney murine leukemia virus (M-MuLV), human T-cell leukemia virus type 1 (HTLV-1), and human T-cell leukemia virus type 2 (HTLV-2). Overall, these INs required specific LTR sequences for optimal catalysis of 3'-processing reactions, as opposed to strand transfer and disintegration reactions. It is of particular note that in strand transfer reactions the sites of integration were similar among the four INs. In the 3'-processing reaction, sequence specificity for each IN was traced to the three nucleotides proximal to the conserved CA. Reactions catalyzed by M-MuLV IN were additionally influenced by upstream regions. The nucleotide requirements for optimal catalysis differed for each IN. HIV-1 IN showed a broad range of substrate specificities, while HTLV-1 IN and HTLV-2 IN had more defined sequence requirements. M-MuLV IN exhibited greater activity with the heterologous LTR substrates than with its own wild-type substrate. This finding was further substantiated by the high levels of activity catalyzed by the IN on modified M-MuLV LTRs. This work suggests that unlike the other INs examined, M-MuLV IN has evolved with an IN-LTR interaction that is suboptimal.
 ...
PMID:Functional identification of nucleotides conferring substrate specificity to retroviral integrase reactions. 899 22

RNA-DNA hybrid model substrates which mimic an intermediate of Moloney murine leukemia virus (M-MuLV) reverse transcription at the stage where the tRNAPro is removed were constructed. This substrate was used to assay the ability of M-MuLV reverse transcriptase (RT) to cleave the RNA portion of the substrate. The cleavage specificities of the cognate M-MuLV RT and the heterologous enzyme from the human immunodeficiency virus type-1 (HIV-1) were compared. M-MuLV and HIV-1 RT recognize and cleave the RNA at distinct positions. The site of the initial RNase H cleavage in vitro was determined using 3' end nearest neighbor analysis of the initial cleavage product. M-MuLV RT/RNase H removed the model tRNAPro between the terminal ribo-A and ribo-C, resulting in a terminal ribo-A attached to the viral DNA, whereas HIV-1 RT/RNase H was shown to cleave at the RNA-DNA junction. Analysis of the DNA over time indicated that the ribo-A is subsequently removed by M-MuLV RT. In vivo analysis from double-LTR circle junctions illustrated that 16 of the 23 clones isolated possessed the predicted junction if complete removal of the tRNA primer were to occur. The predicted junction for complete removal of the tRNA primer was CATT-AATG. One aberrant circle junction was isolated which could result from the use of an alternative primer. In contrast with HIV, no M-MuLV circle junctions were isolated which indicated processing of a single-LTR terminus by integrase. Analysis from in vivo and in vitro studies indicate that the M-MuLV tRNAPro primer is completely removed after plus-strand strong-stop synthesis.
 ...
PMID:RNase H cleavage of tRNAPro mediated by M-MuLV and HIV-1 reverse transcriptases. 912 56

The identification of monogenic and complex genes responsible for neurological disorders requires new approaches for delivering therapeutic protein genes to significant numbers of cells in the central nervous system. A lentivirus-based vector capable of infecting dividing and quiescent cells was investigated in vivo by injecting highly concentrated viral vector stock into the striatum and hippocampus of adult rats. Control brains were injected with a Moloney murine leukemia virus, adenovirus, or adeno-associated virus vector. The volumes of the areas containing transduced cells and the transduced-cell densities were stereologically determined to provide a basis for comparison among different viral vectors and variants of the viral vector stocks. The efficiency of infection by the lentivirus vector was improved by deoxynucleoside triphosphate pretreatment of the vector and was reduced following mutation of integrase and the Vpr-matrix protein complex involved in the nuclear translocation of the preintegration complex. The lentivirus vector system was able to efficiently and stably infect quiescent cells in the primary injection site with transgene expression for over 6 months. Triple labeling showed that 88.7% of striatal cells transduced by the lentivirus vector were terminally differentiated neurons.
 ...
PMID:Highly efficient and sustained gene transfer in adult neurons with a lentivirus vector. 926 86

The majority of human endogenous retroviral HERV-H elements in the human genome have large deletions in pol and lack most of env, 5-10% are more or less complete with a potentially immunosuppressive transmembrane protein-encoding env region. Spliced HERV-H env transcripts were detected in T-cell leukaemia cell lines and lymphocytes from healthy blood donors by using RT-PCR. The transcripts all contained a splice donor in the leader region downstream from the primer-binding site and a previously unreported splice acceptor in the integrase-encoding region of pol, absent in the HERV-H deletion elements. In singly spliced transcripts the leader and integrase regions were joined directly whereas in multiply spliced transcripts they were joined with an alternative exon from the protease-encoding region located between the two regions. env transcripts from three different HERV-H elements were identified: one element similar to a HERV-H consensus sequence was primarily amplified from the T-cell leukaemia cell lines and two other more defective elements were amplified from normal lymphocytes. One of these elements was shown to be a reintegrated spliced transcript where the protease and integrase regions were joined, removing most of pol but leaving gag intact. Other spliced transcripts, joining the protease region and the 3'-LTR, were also amplified. The fact that HERV-H elements with an intact env splice acceptor also use the splice sites in the protease-encoding region suggests that this unusual multiple splice pattern could have a biological function in the intact HERV-H.
 ...
PMID:Spliced human endogenous retroviral HERV-H env transcripts in T-cell leukaemia cell lines and normal leukocytes: alternative splicing pattern of HERV-H transcripts. 934 78

An in vivo integration assay using the expressed human immunodeficiency virus type 1 (HIV-1) integrase (IN) protein and plasmids carrying a copy of the infectious Moloney murine leukemia virus (MuLV) provirus genome as substrates is presented. The HIV-1 IN gene was taken from vector pINSD and cloned into vector pXT1 to give pXT1-IN. Two and three nucleotides from the circle junction on one pair of U3 and U5 attachment (att) sequences on an infectious MuLV provirus vector pMLV-K were changed by means of site-directed mutagenesis to that of the corresponding HIV-1 att sequences to generate vector pMLV*(U3U5). The MuLV IN sequence was partially deleted for vectors pMLV-K and pMLV*(U3U5) to generate vectors pMLV delta IN and pMLV*(U3U5) delta IN. Integration of these wild type and MuLV IN partially deleted or att mutated MuLV provirus vectors in the transfected cells by the expressed HIV-1 IN was monitored by means of a non-radioactive reverse transcriptase (RT) assay for released and collected virions. No RT activity was detected for the NIH/3T3 cell singly transfected with vector pMLV delta IN. However some RT activities were observed for the HIV-1 IN expressing cell transfected either with vectors pMLV delta IN or pMLV*(U3U5) delta IN. This indicated that in the absence of other HIV-1 proteins expressed the MuLV provirus genome was integrated by the expressed HIV-1 IN protein. The integration of these MuLV provirus genomes was further confirmed by polymerase chain reaction analysis on the genomic DNA extracted from the transfected cells using the MuLV IN sequence remained from partial deletion as a target.
 ...
PMID:The genome of Moloney murine leukemia virus can be integrated by the integrase of human immunodeficiency virus type 1 expressed alone in vivo. 936 24

We have probed the nucleoprotein organization of Moloney murine leukemia virus (MLV) pre-integration complexes using a novel footprinting technique that utilizes a simplified in vitro phage Mu transposition system. We find that several hundred base pairs at each end of the viral DNA are organized in a large nucleoprotein complex, which we call the intasome. This structure is not formed when pre-integration complexes are made by infecting cells with integrase-minus virus, demonstrating a requirement for integrase. In contrast, footprinting of internal regions of the viral DNA did not reveal significant differences between pre-integration complexes with and without integrase. Treatment with high salt disrupts the intasome in parallel with loss of intermolecular integration activity. We show that a cellular factor is required for reconstitution of the intasome. Finally, we demonstrate that DNA-protein interactions involving extensive regions at the ends of the viral DNA are functionally important for retroviral DNA integration activity. Current in vitro integration systems utilizing purified integrase lack the full fidelity of the in vivo reaction. Our results indicate that both host factors and long viral DNA substrates may be required to reconstitute an in vitro system with all the hallmarks of DNA integration in vivo.
 ...
PMID:A large nucleoprotein assembly at the ends of the viral DNA mediates retroviral DNA integration. 940 79

This report describes the results of experiments to determine whether chimeras between a retrovirus and portions of Ty3 are active in vivo. A chimera between Ty3 and a Neo(r)-marked Moloney murine leukemia virus (M-MuLV) was constructed. The C-terminal domain of M-MuLV integrase (IN) was replaced with the C-terminal domain of Ty3 IN. The chimeric retroviruses were expressed from an amphotrophic envelope packaging cell line. The virus generated was used to infect the human fibrosarcoma cell line HT1080, and cells in which integration had occurred were selected by G418 resistance. Three independently integrated viruses were rescued. In each case, the C-terminal Ty3 IN sequences were maintained and short direct repeats of the genomic DNA flanked the integration site. Sequence analysis of the genomic DNA flanking the insertion did not identify a tRNA gene; therefore, these integration events did not have Ty3 position specificity. This study showed that IN sequences from the yeast retrovirus-like element Ty3 can substitute for M-MuLV IN sequences in the C-terminal domain and contribute to IN function in vivo. It is also one of the first in vivo demonstrations of activity of a retrovirus encoding an integrase chimera. Studies of chimeras between IN species with distinctive integration patterns should complement previous work by expanding our understanding of the roles of nonconserved domains.
 ...
PMID:A chimeric Ty3/Moloney murine leukemia virus integrase protein is active in vivo. 955 20


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>