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PubMed1992

Exogenous primer-independent cDNA synthesis with commercial reverse transcriptase preparations on plant virus RNA templates.

Upon reverse transcription and cloning manipulations with virion RNAs of several plant viruses, namely beet yellows virus, brome mosaic virus, and potato virus X, we came across a significant background synthesis of cDNA on the virion RNA template in vitro independent of exogenous primers added. When tested with beet yellow virus RNA template, several commercial preparations of avian myeloblastosis virus (AMV) reverse transcriptase showed the background activity monitored by the [alpha-32P]dNTP incorporation in vitro, while the enzyme from murine moloney leukemia virus (MMLV) was found strictly exogenous-primer-dependent. To detect possible nucleic acid contaminations in reverse transcriptase, the enzyme preparations from several commercial sources were incubated with [gamma-32P]ATP and polynucleotide kinase. The labeled material from AMV reverse transcriptase preparations comigrated with a tRNA marker in polyacrylamide gels and was found to be RNase-sensitive. The MMLV reverse transcriptase preparations were free from such a contamination. These results indicate that the exogenous-primer-independent cDNA synthesis by some AMV reverse transcriptases could be due to a contaminating tRNA (or its low-molecular-weight degradation products) serving as an endogenous primer.

Artifacts↗
PubMed1986

Biochemical heterogeneity of reverse transcriptase purified from the AIDS virus, HTLV-III.

The reverse transcriptase from AIDS virus, HTLV-III, was purified and characterized. The purified enzyme has a very high affinity for template primers (rC)n X (dG)12 and (rCm)n X (dG)12 compared to that for (rA)n X (dT)12. In addition, the HTLV-III reverse transcriptase was able to transcribe (rAm)n X (dT)12 very efficiently. The ionic requirements are unique in the sense that HTLV-III reverse transcriptase prefers Mg2+ as divalent ions to transcribe (rC)n X (dG)12 and (rA)n X (dT)12. The Mr of the enzyme is 95 000-98 000. Unlike the HTLV-I reverse transcriptase, the HTLV-III enzyme is highly stable and has a much higher activity in the presence of (rC)n X (dG)12; the Vmax for HTLV-III reverse transcriptase is several-fold higher than that for HTLV-I enzyme. The enzyme activity of the purified reverse transcriptase from HTLV-III was resolved into two peaks on a preparative isoelectric column, one at pH 5.75 and the other at pH 6.25. This leads us to conclude that the reverse transcriptase of HTLV-III is biochemically heterogeneous.

Cations, Divalent↗
PubMed1983

Mechanism of action of the endonuclease associated with the alpha beta and beta beta forms of avian RNA tumor virus reverse transcriptase.

Preparations of the alphabeta and the betabeta forms of reverse transcriptase from the Prague C strain of Rous sarcoma virus grown in chicken embryo fibroblasts, the alphabeta and the betabeta forms of the enzyme from the B77 strain of Rous sarcoma virus grown in duck embryo fibroblasts, and the alphabeta form of reverse transcriptase from avian myeloblastosis virus have been analyzed. All these enzyme preparations contain a Mn(2+) -activated endonuclease activity. The betabeta form of enzyme, in addition, contains a Mg(2+) -dependent endonuclease. Such an activity is barely detectable in the alphabeta form of enzymes. The endonuclease associated with reverse transcriptase introduces single- and double-strand breaks containing 3' OH and 5' P termini into RF I DNA. The conversion of RF I DNA to RF III DNA is more readily catalyzed by the betabeta form of reverse transcriptase. In contrast to a recently published report by Hizi et al. (J. Virol 41:974-981, 1982), we have failed to detect the conversion of RF I DNA to covalently closed relaxed circles (RF IV DNA) by any of the alphabeta form of enzymes tested. RF IV DNA was not produced by the betabeta form of reverse transcriptase either. We conclude that topoisomerization is not an intrinsic activity of reverse transcriptase. Although the conversion of RF I DNA to RF II DNA was found to be rapid, the endonuclease associated with reverse transcriptase acted slowly on RF II, RF III, and RF IV DNAs. Circular and linear single-stranded DNAs were also susceptible to cleavage by the endonuclease at a rate comparable to nicking of RF I DNA. This pattern of activity suggests that the endonuclease cleaves the RF I DNA in the single-stranded regions of the DNA induced by its supercoiling. The preference of the alphabeta and the betabeta forms of the endonuclease for viral DNA was tested with Rous-associated virus type 2 and Rous sarcoma virus transformation-defective Schmidt-Ruppin B strain DNA molecularly cloned in plasmid pBR322 and M13 DNA vectors, respectively. The rate of nicking of RF I DNA containing viral DNA or partial sequences of viral DNA with one or two tandem long terminal repeats was the same as when these sequences were not present in the host vectors. A similar lack of preference was observed with single-stranded M13 DNAs.

Avian Leukosis Virus↗
PubMed1990

Interactions with tRNA(Lys) induce important structural changes in human immunodeficiency virus reverse transcriptase.

Retroviral RNA-dependent DNA polymerase (reverse transcriptase or RT) uses the 3'OH end of a cellular tRNA as primer to initiate DNA synthesis. Previous work with avian retrovirus has shown that reverse transcriptase is implicated in the selection of cellular virion-encapsidated tRNAs and has shown that the primer tRNA is positioned on the primer binding site near the 5' end of the viral RNA. These mechanisms support the idea that the retroviral polymerase should form complexes with primer tRNA and the specific encapsidated ones. The genomic sequence of human immunodeficiency virus (HIV) allows the prediction that tRNA(Lys3) is the natural primer. In this article we show, using the mobility shift assay, that recombinant HIV reverse transcriptase is able to form a complex with bovine tRNA(Lys.) By fluorescence studies and alpha-chymotrypsin analysis we have observed a modification of the enzyme conformation when reverse transcriptase is bound to the putative primer tRNA. This structural change is specific for tRNA(Lys) although the retroviral polymerase is able to interact with other tRNAs.

HIV↗
PubMed1978

Binding of tRNA to reverse transcriptase of RNA tumor viruses.

The interaction of tRNA with the reverse transcriptase (RNA-dependent DNA polymerase) of mammalian RNA viruses, such as Moloney murine leukemia virus and simian sarcoma virus, has been studied. Whereas the purified reverse transcriptase of mammalian viruses sedimented in glycerol gradients as a globular protein with a molecular weight of 70,000, after interaction with tRNA the enzyme cosedimented with a protein of 150,000 molecular weight. The twofold increase in molecular weight could be a result of either two reverse transcriptase molecules complexed with a tRNA or, alternatively, several tRNA molecules bound to a single enzyme polypeptide. The enzyme complexes were dissociated in part upon degradation of the tRNA moiety by pancreatic RNase A. The reverse transcriptase released from virions of Moloney murine leukemia virus, simian sarcoma virus, and avian myeloblastosis virus, by nonionic detergent, migrated faster on glycerol gradients than purified enzyme preparation. This phenomenon was probably due to complex formation between part of the virion enzyme and the tRNA, which is endogenous in virions. Addition of exogenous tRNA was needed, however, to quantitatively complex all the virion reverse transcriptase of Moloney murine leukemia virus and simian sarcoma viruses. The reverse transcriptase of Moloney murine leukemia virus did not show tRNA species specificity in the binding reaction when glycerol gradients were used for assay. Thus, several tRNA species of Escherichia coli, yeast, chicken, and rat origin were able to complex with the enzyme. The species specificity in the interaction between tRNA and avian myeloblastosis virus reverse transcriptase was also examined. We demonstrated that under our experimental conditions, this enzyme binds different tRNA species of E. coli and yeast as well as tRNA of chicken origin.

Animals↗
PubMed1992

Measurement of HIV-1 reverse transcriptase by a nonradioactive assay system.

Reverse transcriptase activity was measured by incorporation of dUMP linked to digoxigenin into a suitable template-primer molecule. Incorporation was monitored by using peroxidase-conjugated Fab fragments directed against digoxigenin. The standard assay measuring incorporation of radiolabeled nucleotides into acid-precipitable material was compared with this new immunochemical assay with regard to its usefulness for testing inhibitors of reverse transcriptase.

Digoxigenin↗
PubMed1990

Inhibition of the p66/p51 form of human immunodeficiency virus reverse transcriptase by tRNA(Lys).

Human immunodeficiency virus (HIV) reverse transcriptase (RT) uses host tRNA(Lys) partially annealed to the primer binding site (PBS) as primer for the initiation of cDNA synthesis. When assaying cDNA synthesis with a template-primer complex formed by an RNA fragment carrying the PBS site and bovine tRNA(Lys) we noticed that an excess of primer tRNA inhibited strongly the DNA polymerase activity of a recombinant HIV RT (p66-p51 heterodimeric form) produced in transformed yeast cells. The same inhibitory effect was observed with animal DNA polymerase alpha, while avian retrovirus RT was neither affected by tRNA(Lys) nor by its specific primer tRNA(Trp). Although the strongest inhibition was observed with tRNA(Lys), other tRNas like tRNA(Phe) and tRNA(Trp) inhibited also the HIV RT, whereas tRNAs specific for valine, proline and glycine had no effect on enzyme activity. Digestion of tRNA(Lys) with pancreatic RNase abolished the inhibition; on the other hand T1 RNase digestion had no effect on the inhibition suggesting a role of the anticodon region in this effect. The 12- and 14-mers corresponding to the anticodon regions of the three bovine tRNA(Lys) isoacceptors inhibited RT activity, indicating that at least an important part of the inhibitory effect could be ascribed to this tRNA region. A strong stimulation of DNA polymerase activity was observed when the effect of tRNA(Lys) was assayed on a recombinant HIV reverse transcriptase produced in a protease deficient yeast strain, which leads to the production of an active p66 enzyme. The same tRNAs that inhibited strongly the heterodimeric form stimulated the p66 form of HIV reverse transcriptase. The results suggest that although both enzymatic forms are able to interact with tRNA(Lys) the topography, as well as the functional implications of the interaction between the precursor and the mature form of HIV reverse transcriptase with the tRNA(Lys) primer, are different.

Base Sequence↗
PubMed1977

Radioimmunoassay for mammalian type C viral reverse transcriptase.

Radioimmunological techniques were applied to the analysis of reverse transcriptase of mammalian type C RNA viruses. The polymerase of Rauscher mouse leukemia virus was purified by ion exchange and sequential affinity chromatography. Radioimmunoassays that utilized the viral enzyme as a probe detected as little as 1 ng of purified polymerase. No cross-reactivity could be demonstrated between the reverse transcriptase and other known virus-coded proteins. By comparing the immunological reactivity of the purified enzyme with the reactivity of detergent-disrupted virions, Rauscher mouse leukemia virus was shown to contain the antigenic equivalent of 40 molecules of reverse transcriptase. In a homologous competition immunoassay, the Rauscher viral enzyme demonstrated type-specific antigenic determinants, which distinguish it from other mouse type C viral polymerases. In a broadly reactive interspecies immunoassay, the reverse transcriptases of a number of mammalian type C viruses were cross-reactive, indicating their shared antigenic determinants. Various treatments that inhibit or inactivated DNA polymerase activity had little or no effect on the immunological properties of the enzyme. Thus, radioimmunoassays should be useful in the search for type C viral reverse transcriptase as a marker of subviral expression.

Cross Reactions↗
PubMed1978

Binding of tryptophanyl-tRNA to the reverse transcriptase of replication-defective avian sarcoma viruses.

The ability of reverse transcriptase to bind to [3H]tryptophanyl-tRNA and to function as DNA polymerase was compared for five temperature-sensitive mutants of avian sarcoma virus. Both activities of the reverse transcriptase were found to be heat labile in LA 335 and LA 336 as compared with the wild-type parents. For the other mutant viruses, LA 338, LA 343, and LA 672, grown at the permissive temperature, the reverse transcriptase was nearly as heat stable as for the wild-type parents in terms of tRNA binding and DNA polymerase. LA 338, LA 343, and LA 672 showed characteristic defects in their reverse transcriptase when propagated at the nonpermissive temperature; namely, tryptophanyl-tRNA binding and DNA polymerase activities were coordinately decreased in these virions. The reduced enzymatic activities were not entirely due to an inactive reverse transcriptase present in the virions, however, but rather lower amounts of enzyme protein incorporated into the virions contributed to the effect, according to assays of reverse transcriptase antigen by radioimmune competition.

Animals↗
PubMed1992

In vitro enzymatic activity of human immunodeficiency virus type 1 reverse transcriptase mutants in the highly conserved YMDD amino acid motif correlates with the infectious potential of the proviral genome.

Reverse transcriptases contain a highly conserved YXDD amino acid motif believed to be important in enzyme function. The second amino acid is not strictly conserved, with a methionine, valine or alanine occupying the second position in reverse transcriptases from various retroviruses and retroelements. Recently, a 3.5-A (0.35-nm) resolution electron density map of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase positioned the YMDD motif within an antiparallel beta-hairpin structure which forms a portion of its catalytic site. To further explore the role of methionine of the conserved YMDD motif in HIV-1 reverse transcriptase function, we have substituted methionine with a valine, alanine, serine, glycine, or proline, reflecting in some cases sequence motifs of other related reverse transcriptases. Wild-type and mutant enzymes were expressed in Escherichia coli, partially purified by phosphocellulose chromatography, and assayed for the capacity to polymerize TTP by using a homopolymeric template [poly(rA)] with either a DNA [oligo(dT)] or an RNA [oligo(U)] primer. With a poly(rA).oligo(dT) template-primer, reverse transcriptases with the methionine replaced by valine (YVDD), serine (YSDD), or alanine (YADD) were 70 to 100% as active as the wild type, while those with the glycine substitution (YGDD) were approximately 5 to 10% as active. A proline substitution (YPDD) completely inactivated the enzyme. With a poly(rA).oligo(U) template-primer, only the activity of mutants with YVDD was similar to that of the wild type, while mutants with YADD and YSDD were approximately 5 to 10% as active as the wild-type enzyme. The reverse transcriptases with the YGDD and YPDD mutations demonstrated no activity above background. Proviruses containing the reverse transcriptase with the valine mutation (YVDD) produced viruses with infectivities similar to that of the wild type, as determined by measurement of p24 antigen in culture supernatants and visual inspection of syncytium formation. In contrast, proviruses with reverse transcriptases containing the YADD and YSDD mutations were less infectious than wild-type virus. These results point to the critical role of methionine of the YMDD motif in the activity of HIV-1 reverse transcriptase and subsequent replication potential of the virus.

Amino Acid Sequence↗
PubMed1989

Identification of a doubly spliced viral transcript joining the separated domains for putative protease and reverse transcriptase of hepatitis B virus.

Hepatitis B virus (HBV), like retroviruses, replicates through reverse transcription. However, the identity and mechanism for the synthesis of HBV reverse transcriptase remain unknown. The open reading frame (ORF) for HBV putative reverse transcriptase (pol), as a consequence of overlapping with the whole ORF of envelope proteins (hepatitis B surface antigens), includes a hypervariable region at the N terminus. Thus, compared with retroviruses, it is unlikely that HBV reverse transcriptase is translated from complete pol ORF in the full-length pregenomic RNA. We have now detected in infected human livers a novel doubly spliced RNA in which one splicing event removed the hypervariable region of the pol gene but retained the conserved region homologous to retroviral reverse transcriptase. The other splicing event deleted the central region of hepatitis B core antigen and thus brought the protease domain which is important for maturation of reverse transcriptase close to that of pol. For this sequence organization, the spliced RNA as the possible template for the synthesis of HBV reverse transcriptase is discussed.

Base Sequence↗
PubMed1975

Protein kinase and its regulatory effect on reverse transcriptase activity of Rous sarcoma virus.

We have studied the effect of protein phosphokinase (EC 2.7.1.37; ATP:protein phosphotransferase) and phosphoprotein phosphatase (EC 3.1.3.16; phosphoprotein phosphohydrolase) on reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) activity of Rous sarcoma virus. Protein kinase from Rous sarcoma virus-transformed chick embryo fibroblasts was purified by DEAE-cellulose chromatography, Sephadex gel filtration, and isoelectric focusing. Purified reverse transcriptase from Rouse sarcoma virus was preincubated with protein kinase and ATP under conditions allowing incorporation of phosphate into substrate protein. After the preincubation, reverse transcriptase activity was assayed in the presence of poly(rA).oligo(dT) as template. A 2- to 5-fold increase of reverse transcriptase activity was found after the preincubation of reverse transcriptase with protein kinase and ATP. Incubation of reverse transcriptase with heat-treated, inactive protein kinase and ATP had no effect on transcriptase activity. When the transcriptase preparation was incubated with protein kinase and [gamma-32P]ATP and subsequently purified by chromatography on phosphocellulose and Sephadex gel filtration, significant amounts of 32P-labeled proteins were found in the fractions exhibiting reverse transcriptase activity, suggesting 32P incorporation into transcriptase or transcriptase-associated proteins. A 20-60% decrease of reverse transcriptase activity was observed after incubation of reverse transcriptase with phosphatase. The results suggest that phosphorylative modification of reverse transcriptase may be critical in the regulation of reverse transcriptase-catalyzed DNA synthesis.

Alkaline Phosphatase↗
PubMed1989

Human immunodeficiency virus 1 reverse transcriptase. Template binding, processivity, strand displacement synthesis, and template switching.

We have analyzed the kinetics of DNA synthesis catalyzed by reverse transcriptase from human immunodeficiency virus 1 (HIV-1). Reverse transcriptase, overproduced in Escherichia coli and purified to homogeneity, has polymerase and RNase H activity. Reverse transcriptase forms a stable complex with poly(rA).oligo(dT) primer-templates in the absence of Mg2+ and dTTP with an equilibrium dissociation constant of 3 nM. Synthesis from these preformed complexes can be initiated, and restricted to a single processive cycle, by the simultaneous addition of Mg2+, dTTP, and excess competitor RNA. Preformed complexes decay with a maximal half-life of 2-3 min. Synthesis on poly(rA) templates is processive with an incorporation rate of 10-15 nucleotides/s at 37 degrees C. Processivity varies widely with the template used, increasing from a few to greater than 300 nucleotides in the order: poly(dA) less than double-stranded DNA less than single-stranded DNA less than single-stranded RNA less than poly(rA). On double-stranded DNA reverse transcriptase catalyzes limited strand-displacement synthesis of up to 50 nucleotides. On RNA-DNA hybrids significant DNA synthesis is observed only after degradation of the RNA strand by the RNase H activity of reverse transcriptase. Intermolecular strand switching occurs with poly(rA) templates. At low ionic strength reverse transcriptase can use multiple templates with a single primer, leading to products of greater than template length. Reverse transcriptase and primer do not have to dissociate during the exchange of template strands, thus allowing processive DNA synthesis across template borders.

DNA, Single-Stranded↗
PubMed1990

Template switching by reverse transcriptase during DNA synthesis.

The ability of reverse transcriptase to make template switches during DNA synthesis is implicit in models of retrovirus genome replication, as well as in recombination and oncogene transduction. In order to understand such switching, we used in vitro reactions with purified nucleic acids and enzymes. The assay system involved the use of an end-labeled DNA primer so as to allow the quantitation of elongation on a donor template relative to the amount of elongation achieved by template switching (by means of sequence homology) when an acceptor template RNA was added. We examined several variables that affected the efficiency of the reaction: (i) the reaction time, (ii) the relative amounts of acceptor and donor template, (iii) the extent of sequence overlap between the donor and acceptor templates, and (iv) the presence or absence of RNase H activity associated with the reverse transcriptase. The basic reaction, with RNA templates and normal reverse transcriptase, yielded as much as 83% template switching. In the absence of RNase H, switching still occurred but the efficiency was lowered. Also, when the donor template was changed from RNA to DNA, there was still switching; not surprisingly, this was largely unaffected by the presence or absence of RNase H. Finally, we examined the action of the RNase H on RNA templates after primary transcription but prior to template switching. We found that in most cases, both ends of the original RNA template were able to maintain an association with the DNA product. This result was consistent with the work of others who have shown that RNase H acts as an endonuclease.

Chromosome Deletion↗
PubMed1982

Differential inhibition of DNA polymerase and RNase H activities of the reverse transcriptase by phosphonoformate.

Three potential inhibitors of reverse transcriptase activities, phosphonoformate (PF), phosphonoacetate (PAA), and ethyl-diethyl phosphonoformate (Et-PF), were compared in this study. Only PF was found to inhibit the DNA polymerase activity of the purified reverse transcriptase of Moloney murine leukemia virus (M-MuLV) and avian myeloblastosis virus (AMV). The degree of DNA polymerase inhibition was linear with PF concentration; 50% inhibition was achieved at 10 muM. Whereas PF inhibited both the RNA and DNA dependent DNA polymerase activities, the RNase H activity of the reverse transcriptase was unaffected. Both the endogenous DNA polymerase activity in detergent disrupted virus and the activity of the purified enzyme with the isolated virus genome 70S RNA were inhibited by PF. However, higher concentrations of PF were needed to inhibit the endogenous reaction. The inhibition by PF appeared to be reversible and noncompetitive with respect to the substrate deoxythymidine triphosphate (dTTP). Addition of PF after the initiation of DNA synthesis immediately arrested the reaction.

Animals↗
PubMed1990

Differential inhibitory effects of various flavonoids on the activities of reverse transcriptase and cellular DNA and RNA polymerases.

Four flavonoids, 5,6,7-trihydroxyflavone (baicalein), 3,3',4',5,7-pentahydroxyflavone (quercetin), 3,3',4',5,6,7-hexahydroxyflavone (quercetagetin) and 3,3',4',5,5',7-hexahydroxyflavone (myricetin), were found to be potent inhibitors of reverse transcriptases from Rauscher murine leukemia virus (RLV) and human immunodeficiency virus (HIV). Under the reaction conditions employed, any one of these flavonoids almost completely inhibited the activity of RLV reverse transcriptase at a concentration of 1 microgram/ml. HIV reverse transcriptase was inhibited by 100%, 100%, 90% and 70% in the presence of 2 micrograms/ml quercetin, myricetin, quercetagetin and baicalein, respectively. The mode of inhibition of these flavonoids was competitive (RLV reverse transcriptase) or partially competitive (HIV reverse transcriptase) with respect to the template.primer complex, (rA)n.(dT), and noncompetitive with respect to the triphosphate substrate, dTTP. The Ki values for RLV reverse transcriptase were found to be 0.37 microM and 0.08 microM for baicalein and quercetin, respectively and those for HIV reverse transcriptase were 2.52 microM, 0.52 microM, 0.46 microM and 0.08 microM for baicalein, quercetin, quercetagetin and myricetin, respectively. Comparative studies with other flavonoids (hydroxyflavones, dihydroxyflavones and polyhydroxyflavones and flavanones) carried out to clarify the structure/activity relationships, revealed that the presence of both the unsaturated double bond between positions 2 and 3 of the flavonoid pyrone ring, and the three hydroxyl groups introduced on positions 5, 6 and 7, (i.e. baicalein) were a prerequisite for the inhibition of reverse transcriptase activity. Removal of the 6-hydroxyl group of baicalein required the introduction of three additional hydroxyl groups at positions 3, 3' and 4' (quercetin), to afford a compound still capable of inhibiting the reverse transcriptase activity. Quercetagetin which contains the structures of both baicalein and quercetin, and myricetin which has the structure of quercetin with an additional hydroxyl group on the 5' position also proved strong inhibitors of reverse transcriptase activity. The inhibition by baicalein of reverse transcriptase is highly specific, whereas quercetin and quercetagetin were also strong inhibitors of DNA polymerase beta and DNA polymerase I, respectively. Myricetin was also a potent inhibitor of both DNA polymerase alpha and DNA polymerase I.

Animals↗
PubMed1975

Specific binding of tryptophan transfer RNA to avian myeloblastosis virus RNA-dependent DNA polymerase (reverse transcriptase).

The ability of tryptophan tRNA (tRNATrp) to initiate reverse transcription of the 70S RNA of avian RNA tumor viruses suggested that the reverse transcriptase (RNA-dependent DNA polymerase; deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase; EC 2.7.7.7) might have a specific binding site for the tRNA. A complex of tRNATrp and the avian myeloblastosis virus reverse transcriptase has been demonstrated using chromatography on Sephadex G-100 columns. Of all the chicken tRNAs, only tRNATrp and a tRNA4Met bind to the enzyme with high enough affinity to be selected from a mixture of the chicken cell tRNAs. The ability of tRNATrp to change the sedimentation rate of the enzyme indicates that tRNATrp is not binding to a contaminant in the enzyme preparation. Treatment of the enzyme with monospecific antibody to reverse transcriptase prevented binding of tRNA as well as inhibited the DNA polymerase activity of the enzyme. The ability of reverse transcriptase to utilize tRNATrp aa a primer for DNA synthesis, therefore, appears to involve a highly specific site on the enzyme.

Animals↗
PubMed1987

Inhibition of viral reverse transcriptase by 2',5'-oligoadenylates.

Viral reverse transcriptase activity was inhibited in a concentration dependent manner by 2',5'-oligoadenylate. Kinetically this inhibition was of a mixed type where 2',5'-oligoadenylate was not strictly competitive with dTTP. The potency of inhibition was more marked in the absence than in the presence of sulfhydryl agents. 2',5'-oligoadenylate had no effect on DNA-dependent E. coli DNA polymerase and was much less active against mammalian DNA polymerases. This is the first report of reverse transcriptase inhibition by an inducible constitutive natural ligand.

Adenine Nucleotides↗