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

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.
 ...
PMID:Interaction of tRNA(Lys-3) with multiple forms of human immunodeficiency virus reverse transcriptase. 137 42

We have analysed the mechanism of ribonuclease H (RNaseH) induced cleavage of a defined RNA-DNA hybrid by human immuno-deficiency virus (HIV-1) reverse transcriptase (RT). An in vitro transcribed RNA labelled at the 3' end was hybridized to a pentadecameric DNA oligonucleotide complementary to an internal region of the RNA. Upon incubation of this RNA-DNA hybrid with recombinant p66 or p66/p51 HIV-1 reverse transcriptase, RT-RNaseH mediated cleavage is observed at most nucleotides within the short hybridized stretch, resulting in a spectrum of RNA fragments extending from the 3' label to this region and differing in length by one nucleotide. The same RNA, this time labelled at the 5' end, yields only one or two major cleavage products corresponding to RNA species extending from the 5' label to the middle of the hybridized region. Such a result can be explained by the action of both endonuclease and 3'----5' exonuclease activities inherent to the C-terminal domain of p66 RT. To investigate how RNaseH cleavage is coupled to reverse transcription, a combination of deoxynucleoside triphosphates was used which allowed controlled extension of the primer DNA. Concomitantly with the elongation of the oligonucleotide primer, RNaseH cleavage proceeds towards the 5' end of the RNA with identical increments, suggesting a simultaneous action of both activities.
 ...
PMID:HIV-1 RT-associated ribonuclease H displays both endonuclease and 3'----5' exonuclease activity. 169 Oct 93

We have prepared a plasmid, pRC-RT, for expression of HXB2 HIV-1 reverse transcriptase (RT) in Escherichia coli (Becerra et al., Biochemistry 30, 11707-11719, 1991). Here we describe the optimization of RT overexpression and its purification. In pRC-RT, the precise RT coding region of HXB2 proviral DNA is flanked by start and stop codons, and expression is driven by the phage lambda pL promoter in a temperature-inducible system. The 64,484-Da RT polypeptide (termed p66) is expressed as approximately 10% of total cell protein after 2 h of induction, and the RT is readily solubilized and purified free of DNA Pol I and to near homogeneity as a homodimer of p66 or as a heterodimer of p66 and p51, resembling the natural enzyme. After achieving appropriate expression of the full-length p66 RT, we next created vectors to express multiple individual segments of the p66 polypeptide. These segments are: a 51,000-Da peptide, representing C-terminal truncation of p66, and several peptides representing consecutive N-terminal, central, and C-terminal segments of p66. The latter peptide, corresponding to the RNase H domain of RT, has been purified in large quantities and is currently under study for solution of its structure by NMR. This peptide is devoid of enzyme activity and of substrate-binding capacity, but exists in solution as a folded globular protein with structure resembling that of E. coli ribonuclease H and that of a similar HIV-1 RT RNase H domain peptide examined by X-ray crystallography (Becerra et al., FEBS Lett. 270, 67-80, 1990). Various other RT peptides described here should prove to be similarly useful for structural studies, as well as other approaches.
 ...
PMID:Expression of polypeptides of human immunodeficiency virus-1 reverse transcriptase in Escherichia coli. 768 63

Previous studies have demonstrated that nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) act as chemical enhancers of human immunodeficiency virus type 1 (HIV-1) RT dimerization. In the current study, we sought to define the role of key residues (101, 103, 108, 181, 188, 190, 225 and 318) in the NNRTI-binding pocket on HIV-1 RT heterodimer stability. Thirteen mutant RTs were constructed and evaluated for p66/p51 RT heterodimer formation using the well-established yeast two-hybrid assay. We found that the mutations K101A, P225H, Y318F and Y318W decreased RT heterodimer stability whereas K103N, V108I, V108W, Y181C, Y188L, G190A, G190E, G190W and P225W increased RT heterodimer stability. While these results demonstrate that residues that comprise the NNRTI-binding pocket contribute to the stability of p66/p51 HIV-1 RT, they did not suggest any obvious correlation between RT dimer stability and the extent of NNRTI resistance. Remarkably, mutations at residue G190 (A, E, W) in the p66 RT subunit were found to dramatically increase heterodimer stability. Notably, the G190W mutation increased RT dimer stability almost to the same extent as did 5 microM efavirenz. In light of these findings, we characterized the in vitro activity of recombinant RT expressing mutations at G190 in the p66 subunit only and compared them with a wild-type enzyme complexed with efavirenz. We found that while mutations at G190 had a significant effect on both the DNA polymerase and ribonuclease H activity of the enzyme, their phenotypic effects did not mirror those induced by efavirenz-binding to RT.
 ...
PMID:Impact of residues in the nonnucleoside reverse transcriptase inhibitor binding pocket on HIV-1 reverse transcriptase heterodimer stability. 1833 60

The interactions of archetypical nucleic acid ligands with the HIV-1 polypurine tract (PPT) RNA:DNA hybrid, as well as analogous DNA:DNA, RNA:RNA and swapped hybrid substrates, were used to probe structural features of the PPT that contribute to its specific recognition and processing by reverse transcriptase (RT). Results from intercalative and groove-binding ligands indicate that the wild-type PPT hybrid does not contain any strikingly unique groove geometries and/or stacking arrangements that might contribute to the specificity of its interaction with RT. In contrast, neomycin bound preferentially and selectively to the PPT near the 5'(rA)(4):(dT)(4) tract and the 3' PPT-U3 junction. Nuclear magnetic resonance data from a complex between HIV-1 RT and the PPT indicate RT contacts within the same regions highlighted on the PPT by neomycin. These observations, together with the fact that the sites are correctly spaced to allow interaction with residues in the ribonuclease H (RNase H) active site and thumb subdomain of the p66 RT subunit, suggest that despite the long cleft employed by RT to make contact with nucleic acids substrates, these sites provide discrete binding units working in concert to determine not only specific PPT recognition, but also its orientation on the hybrid structure.
 ...
PMID:Structural probing of the HIV-1 polypurine tract RNA:DNA hybrid using classic nucleic acid ligands. 1840 Jul 80