Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retroviral Gag proteins are targeted to the plasma membrane, where they play the central role in virion formation. Several studies have suggested that the membrane-binding signal is contained within the amino-terminal matrix sequence; however, the precise location has never been determined for the Gag protein of any retrovirus. In this report, we show that the first 31 residues of human immunodeficiency virus type 1 Gag protein can function independently as a membrane-targeting domain when fused to heterologous proteins. A bipartite membrane-targeting motif was identified, consisting of the myristylated N-terminal 14 amino acids and a highly basic region that binds acidic phospholipids. Replacement of the N-terminal membrane-targeting domain of pp60v-src with that of human immunodeficiency virus type 1 Gag elicits efficient membrane binding and a transforming phenotype. Removal of myristate or the basic region results in decreased membrane binding of Gag-Src chimeras in vitro and impaired virion formation by Pr55gag in vivo. We propose that the N-terminal Gag sequence functions as a targeting signal to direct interaction with acidic phospholipids on the cytoplasmic leaflet of the plasma membrane.
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PMID:Identification of a membrane-binding domain within the amino-terminal region of human immunodeficiency virus type 1 Gag protein which interacts with acidic phospholipids. 813 35

Assembly of human immunodeficiency virus type 1 (HIV-1) particles occurs at the plasma membrane of infected cells. Myristylation of HIV-1 Gag precursor polyprotein Pr55Gag is required for stable membrane binding and for assembly of viral particles. We expressed a series of proteins representing major regions of the HIV-1 Gag protein both with and without an intact myristyl acceptor glycine and performed subcellular fractionation studies to identify additional regions critical for membrane binding. Myristylation-dependent binding of Pr55Gag was demonstrated by using the vaccinia virus/T7 hybrid system for protein expression. Domains within the matrix protein (MA) region downstream of the initial 15 amino acids were required for membrane binding which was resistant to a high salt concentration (1 M NaCl). A myristylated construct lacking most of the matrix protein did not associate with the plasma membrane but formed intracellular retrovirus-like particles. A nonmyristylated construct lacking most of the MA region also was demonstrated by electron microscopy to form intracellular particles. Retrovirus-like extracellular particles were produced with a Gag protein construct lacking all of p6 and most of the nucleocapsid region. These studies suggest that a domain within the MA region downstream from the myristylation site is required for transport of Gag polyprotein to the plasma membrane and that stable plasma membrane binding requires both myristic acid and a downstream MA domain. The carboxyl-terminal p6 region and most of the nucleocapsid region are not required for retrovirus-like particle formation.
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PMID:Identification of human immunodeficiency virus type 1 Gag protein domains essential to membrane binding and particle assembly. 815 85

One strategy for somatic gene therapy for human immunodeficiency virus type 1 (HIV-1) infection is based on the regulated expression of dominant negative mutants of the HIV-1 gag gene. To limit expression of the mutant Gag polypeptide to HIV-1-infected cells, we have constructed a replication-defective retroviral vector that contains a Rev-responsive element. By using this construct we have obviated problems that can be associated with constitutive expression of an exogenous gene, an important step toward developing a human therapy. In uncloned T lymphocytes infected (transduced) with this retroviral construct, HIV-1 replication was inhibited by 94% with a concomitant decrease in the cytopathic effects of the virus. In addition, simian immunodeficiency virus (SIV) replication was also shown to be significantly inhibited, suggesting that this mutant Gag protein may have antiviral efficacy against a broad range of primate lentiviruses and that an SIV/macaque model can be used for further in vivo studies. These results have important implications in assessing the potential of somatic gene therapy in the treatment of HIV-1 infection.
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PMID:A Rev-inducible mutant gag gene stably transferred into T lymphocytes: an approach to gene therapy against human immunodeficiency virus type 1 infection. 817 Sep 64

Sequential overlapping Gag protein-derived oligopeptides of human immunodeficiency virus type 1 (HIV-1) 22 to 24 amino acids long, were synthesized and tested in vitro for antiviral activity. Two synthetic peptides, one derived from the matrix protein p17 (NPGLLETSEGCRQ, amino acids 47 to 59) and one located in the capsid protein p24 (PAATLEEMMTA, amino acids 339 to 349) inhibited the production of infectious virus when added to HIV-1-infected cultures when used in the range of 20 to 200 micrograms/ml. As shown by thin section electron microscopy, peptide treatment resulted in the release of immature, deformed virus particles suggesting that the two peptides interfered with assembly and maturation. Other Gag protein-derived oligopeptides had little or no influence on virus production. To characterize further the functionally active regions we synthesized peptide derivatives with three consecutive amino acids substituted by alanine; they did not cause inhibition. Therefore the regions responsible for inhibition were located between amino acids 50 to 61 in p17, and 342 to 350 in p24. These observations might lead to the development of a new antiviral strategy affecting the late stage of virus replication.
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PMID:Inhibition of infectious human immunodeficiency virus type 1 particle formation by Gag protein-derived peptides. 820 12

To map functional domains in the retroviral Gag protein we have constructed chimeric viruses where regions of the murine leukemia virus (MuLV) Gag protein have been replaced with analogous sequences from human immunodeficiency virus type 1 (HIV-1). Here we describe the chimeric virus MuLV(MAHIV) which contains the HIV-1 matrix (MA) protein in place of the MuLV MA. MuLV(MAHIV) is infectious but grows at a reduced rate compared with wild-type MuLV. We found that the partial defect in replication of the chimeric virus is at a late stage in the viral life cycle. The MuLV(MAHIV) Gag proteins are distributed aberrantly within cells and are not associated with cellular membranes. Unlike MuLV, HIV-1 is able to integrate into growth-arrested cells. Incorporation of the HIV-1 MA, which is known to play a role in infection of nondividing cells, does not enable MuLV(MAHIV) to be expressed in growth-arrested cells. While it possesses no amino acid homology, we found that the HIV-1 MA can efficiently replace the MuLV matrix protein in infection.
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PMID:Functional exchange of an oncoretrovirus and a lentivirus matrix protein. 820 17

The product of the vpr open reading frame of human immunodeficiency virus type 1 (HIV-1) is a 15-kDa, arginine-rich protein that is present in virions in molar quantities equivalent to that of Gag. We report here the results of our investigations into the mechanism by which Vpr is incorporated into virions during assembly in infected cells. For these studies we used an expression vector encoding a Vpr molecule fused at its amino terminus to a nine-amino-acid peptide from influenza virus hemagglutinin. The tagged Vpr expression vector and a vpr mutant HIV-1 provirus were used to cotransfect COS cells, and the resulting virions were tested for the presence of the tagged protein on immunoblots probed with monoclonal antibody against the hemagglutinin peptide. The COS-produced virions were found to contain readily detectable amounts of tagged Vpr and smaller amounts of a putative tagged Vpr dimer. Infectivity of the particles was not altered by incorporation of tagged Vpr. Our results using this system in combination with mutant HIV-1 proviruses suggested that incorporation of Vpr into virions requires the carboxy-terminal Gag protein of HIV-1 (p6) but not gp160, Pol, or genomic viral RNA. In addition, analysis of mutated, tagged Vpr molecules suggested that amino acids near the carboxy terminus (amino acids 84 to 94) are required for incorporation of Vpr into HIV-1 virions. The single cysteine residue near the carboxy terminus was required for production of a stable protein. Arginine residues tested were not important for incorporation or stability of tagged Vpr. These results suggested a novel strategy for blocking HIV-1 replication.
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PMID:Incorporation of Vpr into human immunodeficiency virus type 1 virions: requirement for the p6 region of gag and mutational analysis. 823 Apr 45

A synthetic peptide, RPI 312, that specifically inhibits the protease of the human immunodeficiency virus type 1 (HIV-1) showed a potent inhibition on virus production, maturation, and infectivity. Treatment with this agent prevented the cleavage of Gag protein at the site between p17 and p24 in HIV-1 chronically infected MOLT-4 cells as well as in the released virus. Passage of HIV-1 in the presence of gradually increasing concentrations of this protease inhibitor resulted in emergence of a variant that could evade the drug effects. In the resistant variant the maturation of Gag proteins appeared normal, but its infectivity was reduced compared with that of the parent virus. The nucleotides coding the amino acids at and around the cleavage site between Gag proteins p17 and p24 were not changed. One point mutation (A-->G) at site 2082 of the pol gene that resulted in one amino acid change at site 84 of the protease from isoleucine to valine (I-84-->V) could be detected in the resistant variant. An HIV-1 infectious DNA clone with the I-84-->V mutation also showed reduced sensitivity to this protease inhibitor. The findings that the resistant variant had lower infectivity and was still affected by higher doses of the drug support the speculation that resistance to protease inhibitors may not be as problematic as other drug resistance.
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PMID:Generation and characterization of a human immunodeficiency virus type 1 (HIV-1) mutant resistant to an HIV-1 protease inhibitor. 825 33

The matrix domain of human immunodeficiency virus type 1 Gag polyprotein was studied for its role in virus assembly. Deletion and substitution mutations caused a dramatic reduction in virus production. Mutant Gag polyproteins were myristoylated and had a high affinity for membrane association. Immunofluorescence staining revealed a large accumulation of mutant Gag precursors in the cytoplasm, while wild-type Gag proteins were primarily associated with the cell surface membrane. These results suggest a defect in intracellular transport of the mutant Gag precursors. Thus, in addition to myristoylation, the N-terminal region of the matrix domain is involved in determining Gag protein transport to the plasma membrane. Wild-type Gag polyproteins interacted with and efficiently packaged mutant Gag into virions. This finding is consistent with the hypothesis that intermolecular interaction of Gag polyproteins might occur in the cytoplasm prior to being transported to the assembly site on the plasma membrane.
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PMID:Mutations in the N-terminal region of human immunodeficiency virus type 1 matrix protein block intracellular transport of the Gag precursor. 841 40

One of the six putative accessory genes of bovine immunodeficiency virus (BIV) is similar to those identified as rev in the human immunodeficiency virus and visna virus genomes. To further analyze the BIV rev gene locus, protein, and function, rev cDNAs were cloned and characterized. BIV rev mRNA is derived from the full-length transcript by multiple splicing events and consists of three exons, including the untranslated leader sequence and two coding exons. BIV rev cDNA was expressed in bacteria and in a mammalian in vitro translation expression system. A 23-kDa Rev protein (p23rev) was immunologically detected in lysates from both systems by using an antiserum made to a synthetic Rev peptide. Recombinant p23rev made in bacteria was purified and used to make a polyvalent antiserum. Antisera to Rev peptide and recombinant p23rev immunoprecipitated p23rev from BIV-infected mammalian cells but not from virions. A mammalian expression vector using the BIV rev cDNA was constructed; p23rev was immunoprecipitated with anti-Rev serum from 32P-labeled lysates of monkey cells transfected with this plasmid, demonstrating that BIV Rev is phosphorylated. Immunofluorescence and immunoelectron microscopy with anti-BIV Rev antisera localized Rev in the nucleus and, particularly, in the nucleoli of BIV-infected cells. In functional studies, the expression of BIV Rev was shown to positively regulate the appearance both of Gag protein, which is translated from the unspliced primary viral transcript, and of singly spliced env mRNA but not that of the multiply spliced tat mRNA. These results demonstrate that BIV Rev activity correlates with the known function of lentivirus Rev proteins.
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PMID:Characterization of bovine immunodeficiency virus rev cDNAs and identification and subcellular localization of the Rev protein. 841 41

The Gag protein encoded by Rous sarcoma virus (RSV) is the only viral product required for the process of budding whereby virus particles are formed at the plasma membrane. Deletion analysis of this Gag molecule has revealed several regions (assembly domains) that are important for budding. One of these domains is located at the amino terminus and is needed for membrane binding. Another is located within the carboxy-terminal third of the protein. Though there is little sequence homology among the Gag proteins of unrelated retroviruses, it seemed possible that their assembly domains might be functionally conserved, and to explore this idea, numerous Gag chimeras were made. The results indicate that the first 10 amino acids of the human immunodeficiency virus (HIV) Gag protein can suppress the block to budding caused by deletions in the RSV MA sequence, much as described previously for the first 10 residues from the Src oncoprotein (J.W. Wills, R.C. Craven, R. A. Weldon, Jr., T. D. Nelle, and C.R. Erdie, J. Virol. 65:3804-3812, 1991). In addition, the carboxy-terminal half of the HIV Gag protein was fused to a truncated RSV Gag molecule, mutant Bg-Bs, which is unable to direct core assembly. This chimera was able to produce particles at a rate identical to that of RSV and of a density similar to that of authentic virions. Deletion analysis of the carboxy-terminal chimera revealed two small regions within the HIV NC protein that were sufficient for endowing mutant Bg-Bs with these properties. Chimeras lacking both regions produced particles of a low density, suggesting that these sequences may be involved in the tight packing of Gag molecules during assembly. In a related set of experiments, replacement of the RSV protease with that of HIV resulted in premature processing within the RSV sequence and a block to budding. Particle assembly was restored when the HIV PR activity was inactivated by mutagenesis. Collectively, the data presented here illustrate the functional similarities of Gag proteins from unrelated retroviruses.
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PMID:Functional chimeras of the Rous sarcoma virus and human immunodeficiency virus gag proteins. 841 52


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