Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical properties of the p51 subunit of HIV-1 reverse transcriptase (RT) were studied in order to understand its role in the heterodimeric form p66/p51 found in virions. A recombinant form of RT, p51/p51, expressed in yeast, was purified and characterized. The enzyme was affinity labeled using a 5' modified oligonucleotide primer, covalently linked, that was further elongated in the presence of a radioactive dNTP precursor. We found that the p51 subunit was labeled in the p51/p51 form, thus reflecting its activity, while this subunit was catalytically silent in the heterodimer, since only the p66 subunit was labeled in the latter recombinant form. Processivity studies showed long-sized products synthesized by p51/p51, as in the case of the other RT forms. The effect of primer tRNA(Lys) on the p51/p51 activity showed a strong inhibitory effect in the absence of KCl, similar to that observed with the p66/p51 form, while the same p51/p51 enzyme was strongly stimulated by tRNA(Lys), like RT p66/p66, when KCl was present in the incubation mixture.
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PMID:Biochemical characterization of the p51 sub-unit of human immunodeficiency virus reverse transcriptase in homo- and heterodimeric recombinant forms of the enzyme. 128 Jun

RNase D was recently reported as a new enzymatic activity associated with HIV-1 reverse transcriptase (RT), cleaving RNA at two positions within the double-stranded region of the tRNA primer-viral RNA template complex (Ben-Artzi et al., Proc. Natl. Acad. Sci. USA 89 (1992) 927-931). This would make RNase D a fourth distinct activity of HIV-1 RT, in addition to RNA- and DNA-dependent DNA polymerase and RNase H. Using a specific substrate containing tRNA(Lys,3) hybridized to the primer binding site, we were able to detect the reported RNase D activity in our preparations of recombinant HIV-1 RT. This activity was also present in several active-site mutants of RT, suggesting that it is independent of the RNase H and polymerase functionalities of RT. Furthermore, we found that the cleavage specificity of RNase D is the same as that of RNase III isolated from E.coli. A likely explantation of these results--that the observed RNase D activity is attributable to traces of RNase III contamination--was further strengthened by the finding that the recombinant preparations of HIV-1 RT can specifically cleave a phage T7-derived double-stranded RNA processing signal, which has been used as a model substrate for detection of E.coli RNase III. Moreover, RT purified from an RNase III- strain of E.coli displayed no cleavage of the tRNA primer-RNA template complex.
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PMID:RNase D, a reported new activity associated with HIV-1 reverse transcriptase, displays the same cleavage specificity as Escherichia coli RNase III. 128 Aug 10

The human immunodeficiency virus (HIV) proteins gp120 and gp41 are the principal immune target in HIV infection. One of the most important trends in the study of AIDS is linked to the mapping of sites involving in the binding to the cell receptor CD4 and in the induction of virus-neutralizing antibodies (VNA). Recent studies have revealed that gp120 as the major domain contains inducing type-specific BNA (PND) and a binding region with CD4 (CD4-BR). PND is located in the hypervariable loop of gp120 (residues 301-336 for a BRU strain), and CD4-BR is in the conservation area (residues 410-450). By using the synthetic fragments from these areas (BRU and MN strains) and HIV-infected persons' sera, the authors established that the immune response to PND and CD4-BR is somewhat interrelated: there is a synchronized response of HIV antibodies to peptides from the two regions in ELISA (r = 0.82). For analysis of this phenomenon, experiments with cross-linked immunoreactivity of rabbit antisera to peptides from PND and CD4-BR with homologous and heterologous peptides were performed by applying three control peptides from HIV and hepatitis B virus. It has been found that there is a cross reactivity between rabbit anti-PND (MN, BRU) and anti-CD4-BR abs. Peptide homological analysis revealed common structural elements for PND and CD4-BR despite significant differences in their proposed functions. There is a large amount of positively charged aa within both PND and CD4-BR which may be involved in gp120-CD4 interaction. Acetylation of Lys residues resulted in complete loss of peptide reactivity.
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PMID:[Peptides from the principal neutralizing and CD4-binding domain: similar immunoreactive properties and structure pattern]. 128 21

Previously, we have reported that conjugation of antisense oligonucleotides to poly(L-lysine) (PLL) lowers their inhibitory concentration in several biological models. We have now tested these conjugates for inhibition of human immunodeficiency virus type 1 (HIV-1) replication. PLL-conjugated oligonucleotides complementary to the translation initiation site of Tat protein protect cells from the cytopathic effect of HIV-1 in acute infection assays. The EC50 of conjugates is approximately 0.15 microM, which represents a strong reduction in concentration as compared to nonconjugated oligonucleotides (EC50 = 20 microM). In contrast with most reports in the literature, we have observed sequence specific antiviral effects with PLL conjugates. This was particularly noteworthy in antiviral experiments performed with HIV-1 isolates presenting heterogeneity in the 5' end of the tat mRNA sequence. Two mismatches at the target site were sufficient to reduce very significantly the antiviral activity of the conjugates but did not modify the effect of nonconjugated oligonucleotides. Unlike free oligonucleotides, PLL-conjugated ones do not interfere with virus penetration and/or reverse transcription as demonstrated by polymerase chain reaction (PCR) analysis of viral DNA.
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PMID:Poly(L-lysine)-conjugated oligonucleotides promote sequence-specific inhibition of acute HIV-1 infection. 128 42

Previous studies have indicated that most HLA-A2-binding peptides are 9 amino acid (aa) residues long, with a Leu at position 2 (P2), and a Val or Leu at P9. We compared the binding properties of different peptides by measuring the rate of dissociation of beta 2-microglobulin from peptide-specific HLA-A2 complexes. The simplest peptide that we identified that could form HLA-A2 complexes had the sequence (in single letter aa code) GLFGGGGGV, indicating that three nonglycine aa are sufficient for binding to HLA-A2. To determine whether most nonapeptides that contained Leu at P2 and Val or Leu at P9 could bind to HLA-A2, we tested the binding of nonapeptides selected from published HIV and melanoma protein sequences, and found that six of seven tested formed stable HLA-A2 complexes. We identified an optimal antigenic undecapeptide from the cytomegalovirus gB protein that could form stable HLA-A2 complexes that contained apparent anchor residues at P2 and P11 (sequence FIAGN-SAYEYV), indicating that the spacing between anchor residues can be somewhat variable. Finally, we tested the importance of every aa in the influenza A matrix peptide 58-66 (sequence GILGFVFTL) for binding to HLA-A2, by using Ala-substituted and Lys-substituted peptides. We found that multiple positions were important for stable binding, including P2, P3, P5-P7, and P9. We conclude that the P2 and P9 anchor residues are of prime importance for peptide binding to HLA-A2. However, other peptide side chains (especially at P3) contribute to the stability of the interaction. In certain cases, the optimal length for peptide binding can be longer than 9 residues.
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PMID:Sequence motifs important for peptide binding to the human MHC class I molecule, HLA-A2. 133 Dec 39

We describe a peptide vaccine model based on the mimicry of surface coat protein of a pathogen. This model used a macromolecular assemblage approach to amplify peptide antigens in liposomes or micelles. The key components of the model consisted of an oligomeric lysine scaffolding to amplify peptide antigens covalently 4-fold and a lipophilic membrane-anchoring group to further amplify noncovalently the antigens many-fold in liposomal or micellar form. A peptide antigen derived from the third variable domain of glycoprotein gp120 of human immunodeficiency virus type 1 (HIV-1), consisting of neutralizing, T-helper, and T-cytotoxic epitopes, was used in a macromolecular assemblage model (HIV-1 linear peptide amino acid sequence 308-331 in a tetravalent multiple antigen peptide system linked to tripalmitoyl-S-glycerylcysteine). The latter complex, in liposome or micelle, was used to immunize mice and guinea pigs without any adjuvant and found to induce gp120-specific antibodies that neutralize virus infectivity in vitro, elicit cytokine production, and prime CD8+ cytotoxic T lymphocytes in vivo. Our results show that the macromolecular assemblage approach bears immunological mimicry of the gp120 of HIV virus and may lead to useful vaccines against HIV infection.
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PMID:Macromolecular assemblage in the design of a synthetic AIDS vaccine. 134 73

A synthetic RNA oligonucleotide (15-mer) corresponding to the 3' end of the lysine tRNA primer was hybridized to single-stranded DNA containing the human immunodeficiency virus type 1 (HIV-1) primer-binding site and extended with a DNA polymerase. The resulting structures were used to study primer removal by the RNase H activity of HIV-1 reverse transcriptase. The initial cleavage event removes the RNA primer as a 14-mer and leaves a single ribonucleotide A residue bound to the 5' end of the DNA strand. This result explains the observation by several groups that HIV-1 circle junctions contain 4 bp that are not present in the integrated provirus instead of the predicted 3 bp. Subsequent cleavage events occur at other sites internal to the RNA molecule, and the ribonucleotide A residue on the end of the DNA strand is ultimately removed. Therefore, the biologically relevant cleavage that produces the 14-mer reflects the kinetics of the reaction as well as a specificity for nucleic acid sequence. When the RNA oligonucleotide alone was hybridized to the primer-binding site and tested as a substrate for HIV-1 RNase H, the cleavage pattern near the 3' end of the RNA was altered.
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PMID:Incomplete removal of the RNA primer for minus-strand DNA synthesis by human immunodeficiency virus type 1 reverse transcriptase. 137 87

Primer tRNA regions involved in the interactions between human immunodeficiency virus reverse transcriptase (HIV RT) and tRNA(Lys) were studied by digestion of primer with pancreatic ribonuclease in the presence or absence of HIV RT. The acceptor stem of tRNA(Lys) is not noticeably protected against nuclease action in the presence of HIV RT, while this enzyme clearly protects part of the anticodon and dihydrouridine loops of tRNA(Lys). The acceptor stem of primer tRNA was digested by RNase A only in the presence of the retroviral enzyme, suggesting a partial destabilization of this region by the HIV RT. Synthetic oligoribonucleotides, corresponding to the anticodon and the dihydrouridine loops, inhibited strongly reverse transcription, confirming the strong interaction of these tRNA regions with the enzyme.
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PMID:Preferential interaction of human immunodeficiency virus reverse transcriptase with two regions of primer tRNA(Lys) as evidenced by footprinting studies and inhibition with synthetic oligoribonucleotides. 137 51

Using the murine system we have analyzed an immunogenic T cell peptide epitope corresponding to amino acids 96-112 of the simian immunodeficiency virus-negative regulatory protein sequence. This epitope was unusual in that it was strongly immunogenic in mice of five of the six H-2 haplotypes tested. We generated a T cell hybridoma (SVNF) specific for this peptide in order to determine how manipulating the peptide might alter its immunogenicity. Substitution analysis showed that His 103, Pro 104, Val 106, and Pro 107 were important amino acids for stimulating SVNF because substitutions at these positions diminished the reactivity of SVNF. However, we also found that substituting an Ala for a Val at position 100 or a Val for an Ala at position 110 enhanced reactivity of SVNF. We were able to further enhance the immunogenicity of this epitope by extending the carboxyl terminus two amino acids and making the resulting carboxyl-terminal Lys an amide and by adding a Glu to the amino terminus. These modifications shifted the in vitro activity of SVNF at least two orders of magnitude. We also compared the ability of this modified peptide and the wild-type SIV nef 96-112 to prime a T cell response in vivo. We primed mice with various doses of either the wild-type or the modified peptide and looked at the ability of the draining lymph node cells to proliferate to wild-type peptide. We found that the modified peptide was 10- to 100-fold better at priming a T cell response than the wild-type peptide. Therefore, we were able to create a peptide that was more immunogenic than the wild-type peptide in vivo as well as in vitro. Manipulations such as these that enhance the immunogenicity of T cell epitopes must be considered in developing peptide vaccines against HIV or other infectious agents.
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PMID:Enhancing the immunogenicity of a permissive binding T cell epitope derived from the simian immunodeficiency virus-encoded negative regulatory factor. 137 68

The interaction of several forms (p51, p66, and p66/p51) of recombinant human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) with a synthetic derivative of its cognate replication primer, tRNA(Lys-3), has been determined by gel-mobility shift analysis. While p66/p51 RT is proficient in tRNA binding, preparations of p66 and p51 display only weak binding at elevated protein:tRNA ratios, despite the former containing both RNA-dependent DNA polymerase and ribonuclease H (RNase H) activity. Gel permeation analysis of purified p66 RT indicate this to be predominantly monomeric, suggesting that dimerization may be a prerequisite for efficient tRNA binding. Prolonged incubation of a mixture of the 66- and 51-kDa polypeptides results in heterodimer reconstitution, restoration of tRNA binding, and recovery of appreciable levels of RNA-dependent DNA polymerase activity. Under the same conditions, both the tRNA binding and RNA-dependent DNA polymerase activities of the 66- and 51-kDa polypeptides are unaffected, suggesting that they remain in the monomeric conformation.
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PMID:Interaction of tRNA(Lys-3) with multiple forms of human immunodeficiency virus reverse transcriptase. 137 42


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