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)

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

Early events in the retroviral replication cycle include the conversion of viral genomic RNA into linear double-stranded DNA. This process is mediated by the reverse transcriptase (RT), a multifunctional enzyme that possesses RNA-dependent DNA polymerase, DNA-dependent DNA polymerase, and RNase H activities. In the course of studies of a recombinant RT of human immunodeficiency virus type 1 (HIV-1), we observed an additional, unexpected activity of the enzyme. The purified RT catalyzes a specific cleavage in HIV-1 RNA hybridized to tRNALys, the primer for HIV-1 reverse transcription. The cleavage at the primer binding site (PBS) of HIV RNA is dependent on the double-stranded structure of the HIV RNA-tRNALys complex. This RNase activity appears to be distinct from the RNase H activity of HIV-1 RT, as the substrate specificity and the products of the two activities are different. Moreover, Escherichia coli RNase H and avian myeloblastosis virus RT are unable to cleave the HIV RNA-tRNALys complex. We refer to this unusual activity as RNase D. Two lines of evidence indicate that the specific RNase D activity is an integral part of recombinant HIV RT. The specific RNase D activity comigrates with the other RT activities, DNA polymerase, and RNase H upon filtration on a Superose 6 gel column or chromatography on a phosphocellulose column. Moreover, three recombinant HIV-1 RT preparations expressed and purified in different laboratories by various procedures exhibit RNase D activity. Sequence analysis indicated that RNase D activity cleaves the substrate HIV-1 RNA-tRNALys at two distinct sites within the PBS sequence 5'-UGGCGCCCGA decreases ACAG decreases GGAC-3'. The sequence specificity of RNase D activity suggests that it might be involved in two stages during the reverse transcription process: displacement of the PBS to enable copying of tRNALys sequences into plus-strand DNA or to facilitate the second template switch, which was postulated to occur at the PBS sequence.
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PMID:Double-stranded RNA-dependent RNase activity associated with human immunodeficiency virus type 1 reverse transcriptase. 137 Oct 14