Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gag and pol genes of the human immunodeficiency virus type 1 (HIV-1) (ref. 1) are translated as two polyproteins, Pr55gag and Pr160gag-pol (refs 2-6), which are subsequently cleaved by the action of a virus-encoded protease into the four structural gag proteins of the virion core (p17, p24, p7 and p6) and the pol-encoded enzymes essential for retrovirus replication (protease, reverse transcriptase, ribonuclease H, and endonuclease). Mutational inactivation of the proteases of HIV-1 and other retroviruses results in immature, non-infectious virions, indicating that exogenous inhibition of the protease may represent an attractive approach to anti-AIDS therapy. Here we demonstrate that synthetic peptide analogues, which are potent inhibitors of purified HIV-1 protease, inhibit the processing of the viral polyproteins in cultures of HIV-1-infected T lymphocytes and attenuate viral infectivity.
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PMID:Inhibition of HIV-1 protease in infected T-lymphocytes by synthetic peptide analogues. 168 46

The virally encoded protease of human immunodeficiency virus (HIV) is responsible for specific cleavage events leading to the liberation of the enzymes reverse transcriptase, integrase, ribonuclease H, and the core proteins from the gag-pol and gag polyprotein precursors. Utilizing gag polyprotein synthesized in vitro, we have shown that this substrate is sequentially cleaved by purified HIV protease to yield products that on the basis of their sizes and immunoreactivities correspond to p15, p6, p7, p17, and finally mature p24. We have placed unique restriction sites flanking the p17-p24 domain in order to facilitate replacement of cleavage site sequences by utilizing oligonucleotide cassettes. Replacement of the rapidly cleaved methionine-methionine bond at the p24-p15 junction with tyrosine-proline or replacement of the tyrosine-proline bond at the p17-p24 junction with methionine-methionine results in sites that cannot be efficiently cleaved. A basic amino acid at the p17-p24 scissile bond is not tolerated. Replacement of this cleavage site with an inverted repeat amino acid sequence gives intermediate rates of cleavage. In an attempt to convert the p17-p24 domain into a p24-p15 domain, residues flanking the scissile bond were exchanged in an expanding iterative fashion. When four residues flanking the scissile bond had been replaced, the rate of cleavage relative to that of the native p17-p24 sequence was increased fourfold. The cleavage rate of the native p24-p15 sequence is still some 10-fold greater than that of the p17-p24 sequence, suggesting that more-distant residues significantly affect the cleavage rate.
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PMID:Mutagenesis of protease cleavage sites in the human immunodeficiency virus type 1 gag polyprotein. 198 79

Cytoplasmic extracts prepared from cells infected with metabolically radiolabeled virions of human immunodeficiency virus type 1 contain viral DNA in association with labeled viral proteins. Viral DNA can be purified from these extracts by gel filtration chromatography and sucrose gradient sedimentation as a part of a nucleoprotein complex containing integrase as the only viral protein detectable by immunoprecipitation and gel electrophoretic analysis. The purified complex contains no detectable gag gene products, including p17, p24, p7, or p6, and contains no additional pol gene products, including the p10 protease, p66 and p51 polymerase, or the p15 RNase H. Nearly all of the purified nucleoprotein complexes are capable of integrating into heterologous DNA targets in vitro. These observations demonstrate that integrase is a component of the human immunodeficiency virus type 1 preintegration complex and suggest that integrase may be the only viral protein necessary for the integration of retroviral DNA.
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PMID:Determination of viral proteins present in the human immunodeficiency virus type 1 preintegration complex. 200 49

Reverse transcription of retroviral RNA into double-stranded DNA is catalyzed by reverse transcriptase (RT). A highly conserved polypurine tract (PPT) on the viral RNA serves as primer for plus-strand DNA synthesis and is a possible target for triple-helix formation. Triple-helix formation during reverse transcription involves either single-stranded RNA or an RNA.DNA hybrid. The effect of triple-helix formation on reverse transcription has been analyzed here in vitro using a three-strand-system consisting of an RNA.DNA hybrid and triplex-forming oligonucleotides (TFOs) consisting either of DNA or RNA. Three strand triple-helices inhibit RNase H cleavage of the PPT-RNA.DNA hybrid and initiation of plus-strand DNA synthesis in vitro. Triple-helix formation on a single-stranded RNA target has also been tested in a two-strand-system with TFOs comprising Watson-Crick and Hoogsteen base-pairing sequences, both targeted to the PPT-RNA, on a single strand connected by a linker (T)4. TFOs prevent RNase H cleavage of the PPT-RNA and initiation of plus-strand DNA synthesis in vitro. In cell culture experiments one TFO is an efficient inhibitor of retrovirus replication, leading to a block of p24 synthesis and inhibition of syncytia formation in newly infected cells.
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PMID:Inhibition of HIV-1 reverse transcription by triple-helix forming oligonucleotides with viral RNA. 753 75

The nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI) delavirdine (DLV) selects in vitro for the human immunodeficiency virus type 1 (HIV-1) RT mutation P236L, which confers high-level resistance to DLV but not other NNRTIs. Unexpectedly, P236L has developed infrequently in HIV-1 isolates obtained from patients receiving DLV; K103N is the predominant resistance mutation observed in that setting. We characterized the replication fitness of viruses derived from pNL4-3 containing P236L or K103N in both H9 and primary human peripheral blood mononuclear cell cultures infected in parallel with the two mutants. In the absence of DLV, p24 production by wild-type virus occurred more rapidly and to higher levels than with either mutant; P236L consistently demonstrated a two- to threefold decrease in p24 relative to K103N. At low levels of DLV, growth of wild-type virus was severely inhibited, and K103N replicated two- to threefold more efficiently than P236L. At high concentrations of DLV, P236L replication and K103N replication were both inhibited. Recombinant RTs containing K103N or P236L were analyzed for DNA polymerization on heteropolymeric RNA templates and RNase H degradation of RNA-DNA hybrids. Neither mutant demonstrated defects in polymerization. K103N demonstrated normal RNA 5'-end-directed RNase H cleavage and slowed DNA 3'-end-directed RNase H cleavage compared to wild-type RT. P236L demonstrated slowing of both DNA 3'-end- and RNA 5'-end-directed RNase H cleavage, consistent with its reduced replication efficiency relative to K103N. These data suggest that NNRTI resistance mutations can lead to reductions in the efficiency of RNase H cleavage, which may contribute to a reduction in the replication fitness of HIV-1.
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PMID:The P236L delavirdine-resistant human immunodeficiency virus type 1 mutant is replication defective and demonstrates alterations in both RNA 5'-end- and DNA 3'-end-directed RNase H activities. 1036 32

Each of the human immunodeficiency virus type 1 (HIV-1) pol-encoded enzymes, protease (PR), reverse transcriptase (RT), and integrase (IN), is active only as a dimer (or higher-order oligomer in the case of IN), but only RT comprises subunits of different masses. RT is a heterodimer of 66-kDa and 51-kDa subunits. The latter is formed by HIV PR-catalyzed cleavage of p66 during virion maturation, resulting in the removal of the RNase H (RNH) domain of a p66 subunit. In order to study the apparent need for RT heterodimers in the context of the virion, we introduced a variety of mutations in the RT p51-RNH protease cleavage site of an infectious HIV-1 molecular clone. Surprisingly, rather than leading to virions with increased RT p66 content, most of the mutations resulted in significantly attenuated virus that contained greatly decreased levels of RT that in many cases was primarily p51 RT. IN levels were also reduced in several mutants. However, most mutants showed normal levels of the Pr160(gag-pol) precursor polyprotein, suggesting that reduced virion RT arose from proteolytic instability rather than decreased incorporation. Mutant virion p24 Gag levels were equivalent to wild type, indicating that Gag incorporation and processing were not affected. Repeated passage of MT-2 cells exposed to mutant viruses led to the appearance of virus with improved replication capacity; these virions contained normally processed RT at near-wild-type levels. These results imply that additional proteolytic processing of RT to the p66/p51 heterodimer is essential to provide proteolytic stability of RT during HIV-1 maturation.
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PMID:Virion instability of human immunodeficiency virus type 1 reverse transcriptase (RT) mutated in the protease cleavage site between RT p51 and the RT RNase H domain. 1614 Jul 71