1
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Huber LB, Betz K, Marx A. Reverse Transcriptases: From Discovery and Applications to Xenobiology. Chembiochem 2023; 24:e202200521. [PMID: 36354312 DOI: 10.1002/cbic.202200521] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/09/2022] [Indexed: 11/12/2022]
Abstract
Reverse transcriptases are DNA polymerases that can use RNA as a template for DNA synthesis. They thus catalyze the reverse of transcription. Although discovered in 1970, reverse transcriptases are still of great interest and are constantly being further developed for numerous modern research approaches. They are frequently used in biotechnological and molecular diagnostic applications. In this review, we describe the discovery of these fascinating enzymes and summarize research results and applications ranging from molecular cloning, direct virus detection, and modern sequencing methods to xenobiology.
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Affiliation(s)
- Luisa B Huber
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstrasse 10, 78464, Konstanz, Germany
| | - Karin Betz
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstrasse 10, 78464, Konstanz, Germany
| | - Andreas Marx
- Department of Chemistry, Konstanz Research School Chemical Biology, University of Konstanz, Universitätsstrasse 10, 78464, Konstanz, Germany
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2
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Bhadra S, Maranhao AC, Paik I, Ellington AD. One-Enzyme Reverse Transcription qPCR Using Taq DNA Polymerase. Biochemistry 2020; 59:4638-4645. [PMID: 33275410 DOI: 10.1021/acs.biochem.0c00778] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Taq DNA polymerase, one of the first thermostable DNA polymerases to be discovered, has been typecast as a DNA-dependent DNA polymerase commonly employed for PCR. However, Taq polymerase belongs to the same DNA polymerase superfamily as the Molony murine leukemia virus reverse transcriptase and has in the past been shown to possess reverse transcriptase activity. We report optimized buffer and salt compositions that promote the reverse transcriptase activity of Taq DNA polymerase and thereby allow it to be used as the sole enzyme in TaqMan RT-qPCRs. We demonstrate the utility of Taq-alone RT-qPCRs by executing CDC SARS-CoV-2 N1, N2, and N3 TaqMan RT-qPCR assays that could detect as few as 2 copies/μL of input viral genomic RNA.
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Affiliation(s)
- Sanchita Bhadra
- Department of Molecular Biosciences, College of Natural Sciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Andre C Maranhao
- Department of Molecular Biosciences, College of Natural Sciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Inyup Paik
- Department of Molecular Biosciences, College of Natural Sciences, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Andrew D Ellington
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
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3
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Abstract
DNA polymerases play a central role in biology by transferring genetic information from one generation to the next during cell division. Harnessing the power of these enzymes in the laboratory has fueled an increase in biomedical applications that involve the synthesis, amplification, and sequencing of DNA. However, the high substrate specificity exhibited by most naturally occurring DNA polymerases often precludes their use in practical applications that require modified substrates. Moving beyond natural genetic polymers requires sophisticated enzyme-engineering technologies that can be used to direct the evolution of engineered polymerases that function with tailor-made activities. Such efforts are expected to uniquely drive emerging applications in synthetic biology by enabling the synthesis, replication, and evolution of synthetic genetic polymers with new physicochemical properties.
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4
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Lelyveld VS, O'Flaherty DK, Zhou L, Izgu EC, Szostak JW. DNA polymerase activity on synthetic N3'→P5' phosphoramidate DNA templates. Nucleic Acids Res 2019; 47:8941-8949. [PMID: 31428779 PMCID: PMC6755091 DOI: 10.1093/nar/gkz707] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/29/2019] [Accepted: 08/01/2019] [Indexed: 11/12/2022] Open
Abstract
Genetic polymers that could plausibly govern life in the universe might inhabit a broad swath of chemical space. A subset of these genetic systems can exchange information with RNA and DNA and could therefore form the basis for model protocells in the laboratory. N3'→P5' phosphoramidate (NP) DNA is defined by a conservative linkage substitution and has shown promise as a protocellular genetic material, but much remains unknown about its functionality and fidelity due to limited enzymatic tools. Conveniently, we find widespread NP-DNA-dependent DNA polymerase activity among reverse transcriptases, an observation consistent with structural studies of the RNA-like conformation of NP-DNA duplexes. Here, we analyze the consequences of this unnatural template linkage on the kinetics and fidelity of DNA polymerization activity catalyzed by wild-type and variant reverse transcriptases. Template-associated deficits in kinetics and fidelity suggest that even highly conservative template modifications give rise to error-prone DNA polymerase activity. Enzymatic copying of NP-DNA sequences is nevertheless an important step toward the future study and engineering of this synthetic genetic polymer.
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Affiliation(s)
- Victor S Lelyveld
- Howard Hughes Medical Institute, Department of Molecular Biology, and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Derek K O'Flaherty
- Howard Hughes Medical Institute, Department of Molecular Biology, and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Lijun Zhou
- Howard Hughes Medical Institute, Department of Molecular Biology, and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Enver Cagri Izgu
- Howard Hughes Medical Institute, Department of Molecular Biology, and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jack W Szostak
- Howard Hughes Medical Institute, Department of Molecular Biology, and Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
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5
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Krzywkowski T, Kühnemund M, Wu D, Nilsson M. Limited reverse transcriptase activity of phi29 DNA polymerase. Nucleic Acids Res 2019; 46:3625-3632. [PMID: 29554297 PMCID: PMC5909454 DOI: 10.1093/nar/gky190] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 03/13/2018] [Indexed: 01/28/2023] Open
Abstract
Phi29 (Φ29) DNA polymerase is an enzyme commonly used in DNA amplification methods such as rolling circle amplification (RCA) and multiple strand displacement amplification (MDA), as well as in DNA sequencing methods such as single molecule real time (SMRT) sequencing. Here, we report the ability of phi29 DNA polymerase to amplify RNA-containing circular substrates during RCA. We found that circular substrates with single RNA substitutions are amplified at a similar amplification rate as non-chimeric DNA substrates, and that consecutive RNA pyrimidines were generally preferred over purines. We observed RCA suppression with higher number of ribonucleotide substitutions, which was partially restored by interspacing RNA bases with DNA. We show that supplementing manganese ions as cofactor supports replication of RNAs during RCA. Sequencing of the RCA products demonstrated accurate base incorporation at the RNA base with both Mn2+ and Mg2+ as cofactors during replication, proving reverse transcriptase activity of the phi29 DNA polymerase. In summary, the ability of phi29 DNA polymerase to accept RNA-containing substrates broadens the spectrum of applications for phi29 DNA polymerase-mediated RCA. These include amplification of chimeric circular probes, such as padlock probes and molecular inversion probes.
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Affiliation(s)
- Tomasz Krzywkowski
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, SE-171 65, Sweden
| | - Malte Kühnemund
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, SE-171 65, Sweden
| | - Di Wu
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, SE-171 65, Sweden
| | - Mats Nilsson
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Solna, SE-171 65, Sweden
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6
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Furutani S, Nagai H, Takamura Y, Aoyama Y, Kubo I. Detection of expressed gene in isolated single cells in microchambers by a novel hot cell-direct RT-PCR method. Analyst 2012; 137:2951-7. [PMID: 22234623 DOI: 10.1039/c2an15866c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In order to be able to detect the expression of a gene in individual cells, the ability to isolate and lyse a single cell and to perform reverse transcription polymerase chain reaction (RT-PCR) in one device is important. As is common, when performing cell lysis and RT-PCR in the same reaction chamber, it is necessary to add the reagent for RT-PCR after cell lysis. In this study, we propose an original formula for cell lysis and RT-PCR in the same reaction chamber without the addition of reagent by only a heat process, which we termed hot cell-direct RT-PCR. Hot cell-direct RT-PCR was enabled by using Tth DNA polymerase, which is a thermostable polymerase and has high reverse transcription activity in the presence of manganese ions. Direct detection of RT-PCR products was performed by detecting fluorescence with the use of a double-dye fluorescent probe. We attempted to detect the mRNA of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene in isolated Jurkat cells on a microfluidic device, which we had already developed for single cell isolation. After cell isolation and successive hot cell-direct RT-PCR on the device, fluorescent signals from RT-PCR products for a single cell were detected and differentiated from the chamber containing no cells. A highly positive linear relationship (r = 0.9933) was observed between the number of chambers containing cell(s) and those containing RT-PCR products from 10 to 400 cells μL(-1). Thus it was possible to use the novel hot cell-direct RT-PCR method to detect the expressed gene in isolated cells.
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Affiliation(s)
- Shunsuke Furutani
- Graduate School of Engineering, Soka University, Hachioji, Tokyo 192-8577, Japan
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7
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Bessaud M, Autret A, Jegouic S, Balanant J, Joffret ML, Delpeyroux F. Development of a Taqman RT-PCR assay for the detection and quantification of negatively stranded RNA of human enteroviruses: evidence for false-priming and improvement by tagged RT-PCR. J Virol Methods 2008; 153:182-9. [PMID: 18706930 DOI: 10.1016/j.jviromet.2008.07.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Revised: 07/09/2008] [Accepted: 07/17/2008] [Indexed: 11/28/2022]
Abstract
Human enteroviruses are among the most common viruses infecting humans. These viruses are known to be able to infect a wide range of tissues and are believed to establish persistent infections. Enteroviruses are positive-sense single-stranded RNA viruses whose replication involves the synthesis of negative strand intermediates. Therefore, the specific detection of negatively stranded viral RNA in tissues or cells is a reliable marker of active enteroviral replication. The present report presents the development of a real-time RT-PCR allowing the specific detection and quantification of negatively stranded viral RNA. Since it was known that specific amplification of single-stranded RNA can be made difficult by false-priming events leading to false-positive or overestimated results, the assay was developed by using a tagged RT primer. This tagged RT-PCR was shown to be able to amplify specifically negative RNA of enteroviruses grown in cell cultures by preventing the amplification of cDNAs generated by false-priming.
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Affiliation(s)
- Maël Bessaud
- Unité postulante de biologie des virus entériques, Institut Pasteur, 25 rue du Dr Roux, 75 015 Paris, France.
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8
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Mildvan AS, Grisham CM. The role of divalent cations in the mechanism of enzyme catalyzed phosphoryl and nucleotidyl transfer reactions. STRUCTURE AND BONDING 2007. [DOI: 10.1007/bfb0116490] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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9
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DeStefano JJ, Raja A, Cristofaro JV. In vitro strand transfer from broken RNAs results in mismatch but not frameshift mutations. Virology 2000; 276:7-15. [PMID: 11021989 DOI: 10.1006/viro.2000.0533] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An in vitro system to compare the fidelity of strand transfers from truncated vs full-length RNAs was constructed. A donor RNA, on which reverse transcriptase (RT)-directed DNA synthesis was initiated, shared homology with an acceptor RNA, to which DNAs initiated on the donor could transfer. All RNAs were derived from the N-terminal portion of the alpha-lac gene. On full-length donors, transfers occurred when DNAs migrated to the acceptor prior to being completed on the donor. On donors that were truncated, most transfers occurred after DNAs reached the end of the donor. Transfer products were amplified by PCR and used to replace the corresponding region in a vector containing the alpha-lac gene. Transformed Escherichia coli were screened for alpha-complementation by blue-white phenotype analysis, with white colonies scored as those with errors in alpha-lac. These errors were derived from RT synthesis and strand transfer. The mutant colony frequency approximately doubled for transfer products derived from truncated donors (0.026+/-0.005 vs. 0.053+/-0.011 (three experiments +/- SD), for full-length vs. truncated, respectively). The increases resulted from additional non-template-directed bases (mostly thymidines) added to the DNAs before transfer. Sequence analysis of DNAs synthesized on truncated donors showed that about 60% had additions (20/34); however, those without additions transferred at a much higher rate than those with. Transfer of the DNAs with additions always resulted in substitutions; no frameshifts were observed. Results are consistent with RT adding nontemplated nucleotides at template termini. Transfer and subsequent extension of these products is severely inhibited relative to products without additions. The potential relevance of these findings to retrovirus replication is discussed.
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Affiliation(s)
- J J DeStefano
- Department of Cell Biology and Molecular Genetics, University of Maryland College Park, College Park, Maryland 20742, USA.
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DeStefano J, Ghosh J, Prasad B, Raja A. High fidelity of internal strand transfer catalyzed by human immunodeficiency virus reverse transcriptase. J Biol Chem 1998; 273:1483-9. [PMID: 9430686 DOI: 10.1074/jbc.273.3.1483] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
A system to study the fidelity of internal strand transfer events was constructed. A donor RNA, on which reverse transcriptase (RT)-directed DNA synthesis was initiated, shared homology with an acceptor RNA, to which DNAs initiated on the donor could transfer. The homology occurred over a 119-base internal region of the donor which coded for the N-terminal portion of the alpha-lac gene. Polymerase chain reaction (PCR) was used to amplify DNA synthesis products. The PCR products were then digested with PvuII and EcoRI and ligated into a vector which had this same region excised. Transformed Escherichia coli were screened for the ability to produce a functional beta-galactosidase protein by blue-white phenotype analysis with white colonies scored as those with errors in alpha-lac. Products synthesized on the donor were used to assess the error rate of human immunodeficiency virus-RT while products transferring to and subsequently extended on the acceptor (transfer products) were used to monitor transfer fidelity. Human immunodeficiency virus-RT made approximately 1 error per 7500 bases copied in the assay. Nucleocapsid protein (NCp), although stimulating strand transfer 3-fold, had no effect on RT fidelity. Transfer products in the absence of NCp had essentially the same amount of errors as donor-directed products while those produced with NCp showed a slight increase in error frequency. Overall, strand transfer events on this template were highly accurate. Since experiments with other templates have suggested that transfer is error prone, the fidelity of strand transfer may be highly sequence dependent.
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Affiliation(s)
- J DeStefano
- Department of Microbiology, University of Maryland, College Park 20742, USA.
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11
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De Falco M, Grippo P, Rossi M, Orlando P. Multiple forms of DNA polymerase from the thermo-acidophilic eubacterium Bacillus acidocaldarius: purification, biochemical characterization and possible biological role. Biochem J 1998; 329 ( Pt 2):303-12. [PMID: 9425113 PMCID: PMC1219045 DOI: 10.1042/bj3290303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Two DNA polymerase isoenzymes, called DpA and DpB on the basis of their elution order from DEAE cellulose, were purified to homogeneity from the thermo-acidophilic eubacterium Bacillus acidocaldarius. The enzymes are weakly acidophilic proteins constituted by a single subunit of 117 and 103 kDa respectively. DpA and DpB differ in thermostability, in thermophilicity, in sensitivity to assay conditions and in resistance to sulphydryl-group blocking agents such as N-ethylmaleimide and p-hydroxymercuriobenzoate. They differ also in synthetic template-primer utilization, in the apparent Km for dNTPs and in processivity. In particular, DpA utilizes more effic iently synthetic templates-primers such as poly(dA).poly(dT), poly(dT). (rA)12-18 and poly(rA).(dT)12-18 and presents a greater tendency to accept dNTP analogues modified in the sugar or in the base ring, such as cytosine beta-d-arabinofuranoside 5'-triphosphate, 2',3'-dideoxyribonucleosides 5'-triphosphate, butylphenyl-dGTP and digoxigenin-conjugated dUTP. In addition, DpA presents an exonuclease activity that preferentially hydrolyses DNA in the 5'-3' direction, whereas DpB lacks this activity. The possible biological role of the enzymes is discussed.
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Affiliation(s)
- M De Falco
- Istituto di Biochimica delle Proteine ed Enzimologia del Consiglio Nazionale delle Ricerche, Via Toiano 6, 80072 Arco Felice, Naples, Italy
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12
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Kamath-Loeb AS, Hizi A, Tabone J, Solomon MS, Loeb LA. Inefficient repair of RNA x DNA hybrids. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 250:492-501. [PMID: 9428703 DOI: 10.1111/j.1432-1033.1997.0492a.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
RNA x DNA hybrids are commonly observed during normal biological processes. We tested the ability of three DNA-repair enzymes to remove lesions from the DNA strand of RNA x DNA heteroduplexes. Three nucleotide analogs, 5-hydroxy-2'-deoxycytidine triphosphate, 8-oxo-2'-deoxyguanosine triphosphate, and O6-methyl-2'-deoxyguanosine triphosphate, representative of lesions generated by oxygen damage and methylating agents, were incorporated into the DNA strand synthesized using either a DNA or RNA template. The extended DNA x DNA and RNA x DNA hybrids were used as substrates for bacterial formamidopyrimidine-DNA glycosylase, Nth protein (endonuclease III) and O6-methylguanine-DNA methyltransferase. We show that all three lesions are readily cleaved from the DNA strand of a DNA x DNA duplex but are relatively resistant to cleavage when present in the DNA strand of an RNA x DNA hybrid. Our in vitro studies suggest that damaged DNA in RNA x DNA hybrids is less likely to be repaired in vivo.
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Affiliation(s)
- A S Kamath-Loeb
- Department of Pathology, University of Washington, Seattle 98195, USA
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13
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Hizi A, Kamath-Loeb AS, Rose KD, Loeb LA. Mutagenesis by human immunodeficiency virus reverse transcriptase: incorporation of O6-methyldeoxyguanosine triphosphate. Mutat Res 1997; 374:41-50. [PMID: 9067414 DOI: 10.1016/s0027-5107(96)00217-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The high frequency of incorporation of non-complementary nucleotides by HIV-1 reverse transcriptase is likely to be a major factor in the exceptionally rapid accumulation of viral mutations during the course of AIDS infections. To investigate whether this high level of infidelity is also associated with the incorporation of nucleotide analogs, we analyzed O6-methyldeoxyguanosine triphosphate and compared the incorporation of this analog by HIV-1 reverse transcriptase to that catalyzed by other DNA synthesizing enzymes. Our results indicate that O6-methyldeoxyguanosine triphosphate serves as a substrate for DNA synthesized in vitro by HIV-1 RT on both DNA and RNA templates. The product DNA contains the modified purine; it is sensitive to the repair enzyme, O6-methylguanine methyltransferase, which specifically reacts with DNA containing methylated guanines at the O6 position. Using a forward mutation assay we demonstrated that the nucleotide analog incorporated by HIV-1 RT is mutagenic. The mutations produced are single-base substitutions opposite template thymidines and result in A:T --> G:C transitions. The incorporation of a mutagenic nucleotide by HIV-1 RT highlights the possibility of increasing the rate of mutagenesis of HIV by the use of nucleotides that form non-complementary base pairs at high frequency.
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Affiliation(s)
- A Hizi
- Department of Pathology, University of Washington, Seattle 98195, USA
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14
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Jones MD. Reverse transcription of mRNA by Thermus aquaticus DNA polymerase followed by polymerase chain reaction amplification. Methods Enzymol 1993; 218:413-9. [PMID: 7685468 DOI: 10.1016/0076-6879(93)18033-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- M D Jones
- Department Virology, Royal Postgraduate Medical School, Hammersmith Hospital, University of London, England
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15
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Lazcano A, Valverde V, Hernández G, Gariglio P, Fox GE, Oró J. On the early emergence of reverse transcription: theoretical basis and experimental evidence. J Mol Evol 1992; 35:524-36. [PMID: 1282161 DOI: 10.1007/bf00160213] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Reverse transcriptase (RT) was first discovered as an essential catalyst in the biological cycle of retroviruses. However, in the past years evidence has accumulated showing that RTs are involved in a surprisingly large number of RNA-mediated transpositional events that include both viral and nonviral genetic entities. Although it is probable that some RT-bearing genetic elements like the different types of AIDS viruses and the mammalian LINE family have arisen in recent geological times, the possibility that reverse transcription first took place in the early Archean is supported by (1) the hypothesis that RNA preceded DNA as cellular genetic material; (2) the existence of homologous regions of the subunit tau of the E. coli DNA polymerase III with the simian immunodeficiency virus RT, the hepatitis B virus RT, and the beta' subunit of the E. coli RNA polymerase (McHenry et al. 1988); (3) the presence of several conserved motifs, including a 14-amino-acid segment that consists of an Asp-Asp pair flanked by hydrophobic amino acids, which are found in all RTs and in most cellular and viral RNA polymerases. However, whether extant RTs descend from the primitive polymerase involved in the RNA-to-DNA transition remains unproven. Substrate specificity of the AMV and HIV-1 RTs can be modified in the presence of Mn2+, a cation which allows them to add ribonucleotides to an oligo (dG) primer in a template-dependent reaction. This change in specificity is comparable to that observed under similar conditions in other nucleic acid polymerases. This experimentally induced change in RT substrate specificity may explain previous observations on the misincorporation of ribonucleotides by the Maloney murine sarcoma virus RT in the minus and plus DNA of this retrovirus (Chen and Temin 1980). Our results also suggest that HIV-infected macrophages and T-cell cells may contain mixed polynucleotides containing both ribo- and deoxyribonucleotides. The evolutionary significance of these changes in substrate specificities of nucleic acid polymerases is also discussed.
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Affiliation(s)
- A Lazcano
- Departamento de Biología, Facultad de Ciencias-UNAM, México, D.F
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16
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Abstract
The genomic hypervariation of human immunodeficiency virus 1 (HIV-1) could result from misincorporations by the viral reverse transcriptase. We developed an assay for reverse transcriptase fidelity during RNA-dependent as well as DNA-dependent DNA polymerization in vitro. A lacZ alpha RNA fragment transcribed by T3 RNA polymerase was used to mimic first-strand reverse transcription. The corresponding DNA template was used to examine errors by reverse transcriptase during second-strand DNA synthesis. With both templates, the mutations introduced by reverse transcriptase were identified by their mutant phenotypes in an M13 lacZ alpha-complementation assay. We found that the reverse transcriptase from human immunodeficiency virus 1 (HIV-1 RT) was less accurate than the reverse transcriptase from Moloney murine leukemia virus (MLV RT) or the Klenow fragment of Escherichia coli DNA polymerase I (Pol I) on either RNA or DNA templates. The frequency of misincorporation by HIV-1 RT was 1 in 6900 nucleotides polymerized on the RNA template and 1 in 5900 on the DNA template. The error rates of MLV RT and Pol I on the RNA template were less than 1 in 28,000 and 37,000, respectively. The most frequent mutations produced by HIV-1 RT copying the RNA template were C----T transitions and G----T transversions resulting from misincorporation of dAMP.
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Affiliation(s)
- J P Ji
- Joseph Gottstein Memorial Cancer Research Laboratory, Department of Pathology, University of Washington, Seattle 98195
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17
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Myers TW, Gelfand DH. Reverse transcription and DNA amplification by a Thermus thermophilus DNA polymerase. Biochemistry 1991; 30:7661-6. [PMID: 1714296 DOI: 10.1021/bi00245a001] [Citation(s) in RCA: 333] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A recombinant DNA polymerase derived from the thermophilic eubacterium Thermus thermophilus (Tth pol) was found to possess very efficient reverse transcriptase (RT) activity in the presence of MnCl2. Many of the problems typically associated with the high degree of secondary structure present in RNA are minimized by using a thermostable DNA polymerase for reverse transcription, and predominantly full-length products can be obtained. The cDNA can also be amplified in the polymerase chain reaction (PCR) with the same enzyme. The Tth pol was observed to be greater than 100-fold more efficient in a coupled RT/PCR than the analogous DNA polymerase from Thermus aquaticus (Taq pol). The sensitivity of the reactions performed by Tth pol allowed for the detection of ethidium bromide stained products starting with as little as 100 copies of synthetic cRNA. Similar results were also obtained with RNA from a Philadelphia-chromosome positive cell line. Detection of IL-1 alpha mRNA was possible starting with 80 pg of total cellular RNA. The ability of Tth pol to perform both reverse transcription and DNA amplification will undoubtedly prove useful in the detection, quantitation, and cloning of cellular and viral RNA.
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Affiliation(s)
- T W Myers
- PCR Division, Cetus Corporation, Emeryville, California 94608
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18
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Bej AK, Mahbubani MH, Atlas RM. Amplification of nucleic acids by polymerase chain reaction (PCR) and other methods and their applications. Crit Rev Biochem Mol Biol 1991; 26:301-34. [PMID: 1718663 DOI: 10.3109/10409239109114071] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The in vitro replication of DNA, principally using the polymerase chain reaction (PCR), permits the amplification of defined sequences of DNA. By exponentially amplifying a target sequence, PCR significantly enhances the probability of detecting target gene sequences in complex mixtures of DNA. It also facilitates the cloning and sequencing of genes. Amplification of DNA by PCR and other newly developed methods has been applied in many areas of biological research, including molecular biology, biotechnology, and medicine, permitting studies that were not possible before. Nucleic acid amplification has added a new and revolutionary dimension to molecular biology. This review examines PCR and other in vitro nucleic acid amplification methodologies--examining the critical parameters and variations and their widespread applications--giving the strengths and limitations of these methodologies.
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Affiliation(s)
- A K Bej
- Department of Biology, University of Alabama, Birmingham 35294
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19
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Abstract
A peculiar type of satellite DNA, called msDNA, has been discovered in myxobacteria and some natural isolates of E. coli. These molecules are characterized by the presence of single-stranded DNA branching out from an internal guanosine residue of an RNA molecule by a unique 2',5'-phosphodiester linkage. Reverse transcriptase is required for the synthesis of msDNA. The discovery of retroelements in bacterial populations raises many intriguing questions concerning the evolutionary origin of reverse transcriptase, the function and the biosynthesis of msDNA, and the nature of the mechanisms generating the extensive diversity found in msDNA and reverse transcriptase genes among different bacterial strains.
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Affiliation(s)
- M Inouye
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Rutgers, Piscataway 08854
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Reverse transcriptase from Escherichia coli exists as a complex with msDNA and is able to synthesize double-stranded DNA. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38915-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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21
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Tse WT, Forget BG. Reverse transcription and direct amplification of cellular RNA transcripts by Taq polymerase. Gene X 1990; 88:293-6. [PMID: 2347496 DOI: 10.1016/0378-1119(90)90047-u] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We report the ability of Taq polymerase to directly transcribe RNA templates in vitro. We have made use of this finding to develop a single-step protocol for amplification of RNA transcripts. The method was shown to require only subnanogram amounts of total cellular RNA as starting material. A microassay was developed in which RNA can be extracted from one drop of blood or 1000 cultured cells, and analyzed for the expression of a specific gene.
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Affiliation(s)
- W T Tse
- Department of Human Genetics, Yale University School of Medicine, New Haven, CT 06510
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22
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Jones MD, Foulkes NS. Reverse transcription of mRNA by Thermus aquaticus DNA polymerase. Nucleic Acids Res 1989; 17:8387-8. [PMID: 2478963 PMCID: PMC334993 DOI: 10.1093/nar/17.20.8387] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- M D Jones
- Royal Postgraduate Medical School, London, UK
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23
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Singer B, Kuśmierek JT, Fraenkel-Conrat H. In vitro discrimination of replicases acting on carcinogen-modified polynucleotide templates. Proc Natl Acad Sci U S A 1983; 80:969-72. [PMID: 6573665 PMCID: PMC393509 DOI: 10.1073/pnas.80.4.969] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Three different poly(dC)s with modifications that block the N-3 of deoxycytidine were used as templates for polymer synthesis by Escherichia coli DNA polymerase I (EC 2.7.7.7). In contrast to previously reported results with transcriptases, the hydrated form of 3,N(4)-ethenodeoxycytidine (epsilondC.H(2)O) did not mispair. Both 3,N(4)-ethenodeoxycytidine (epsilondC) and 3-methyldeoxycytidine (m(3)dC) led to dTMP misincorporation: 1/20 epsilondC and 1/80 m(3)dC. No other misincorporations appeared to be significant in amount. Thus, both qualitatively and quantitatively, replication errors resulting from carcinogen-modified bases are less frequent than errors in transcription of the same deoxypolynucleotides. Replication of comparable ribopolynucleotide templates by cucumber RNA-dependent RNA polymerase (EC 2.7.7.48) was strongly inhibited by epsilonrC.H(2)O and epsilonrC, so that the fidelity of this enzyme could not be assessed. However, both poly(dC) and poly(rC) containing dU or rU led to incorporation of rA. The presence of even small amounts of purines in poly(rC) greatly depressed synthesis, but the complementary base was incorporated. The finding that an RNA replicase can utilize a deoxypolynucleotide template is a further indication that, at least in vitro, the specificity of the relationship of enzymes and their natural templates is not absolute.
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24
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Andzhaparidze OG, Drynov ID, Bogomolova NN, Chelyapov NV, Boriskin YS. Tick-borne encephalitis virus-specified sequences in persistently infected cell culture revealed by DNA-DNA hybridization. EXPERIENTIA 1979; 35:601-2. [PMID: 376334 DOI: 10.1007/bf01960344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Hybridization of DNA probe, obtained through DNA polymerase-mediated in vitro transcription of tick-borne encephalitis virus (TBEV) RNA, with DNA isolated from persistently infected with TBEV cell culture revealed 5.4 copies of viral genome per haploid set.
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25
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Surrey S, Chambers JS, Muni D, Schwartz E. Restriction endonuclease analysis of human globin genes in cellular DNA. Biochem Biophys Res Commun 1978; 83:1125-31. [PMID: 708430 DOI: 10.1016/0006-291x(78)91512-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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26
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Nazarenko IA, Potapov VA, Romaschenko AG, Salganik RI. Separation of the enzyme catalyzing polymerization of deoxyribonucleoside diphosphates from the preparations of Escherichia coli DNA polymerase I. FEBS Lett 1978; 86:201-4. [PMID: 342272 DOI: 10.1016/0014-5793(78)80562-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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27
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28
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METZLER DAVIDE. Biochemical Genetics and the Synthesis of Nucleic Acids and Proteins. Biochemistry 1977. [DOI: 10.1016/b978-0-12-492550-2.50020-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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29
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Proudfoot NJ. Sequence analysis of the 3' non-coding regions of rabbit alpha- and beta-globin messenger RNAs. J Mol Biol 1976; 107:491-525. [PMID: 63556 DOI: 10.1016/s0022-2836(76)80080-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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30
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Helfman WB, Hendler SS, Smith DW. Escherichia coli DNA polymerases II and III: activation by magnesium or by manganous ions. BIOCHIMICA ET BIOPHYSICA ACTA 1976; 447:175-87. [PMID: 788784 DOI: 10.1016/0005-2787(76)90341-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Escherichia coli DNA polymerases II and III have been extensively studied in vitro when activated with Mg2+. The Mn2+-activated polymerization reactions are considered here, and shown to differ from the Mg2+-activated reactions. The Mn2+-activated DNA polymerase II reaction requires K+ or spermidine, and the effects of monovalent cation and polyamine are additive. In contrast, the Mg2+-activated reaction does not require, but is stimulated by, K+ or spermidine, in a non-additive manner. Under optimal conditions, DNA polymerase II is activated better with Mn2+ than it is with Mg2+, suggesting a physiological role for the Mn2+-activated enzyme. The observed preference for Mn2+ over Mg2+ in reaction kinetics and at high DNA template concentrations suggest that Mg2+ may preferentially activate the associated exonuclease activity. At 29 degrees C, the Mn2+-activated DNA polymerase III reaction is stimulated by K+ and inhibited by ethanol or phosphatidylethanolamine. In contrast, the latter compounds and Triton X-100 increase the initial rate of the Mg2+-activated reaction, whereas K+ inhibits this reaction at all concentrations. The K+ inhibition is reduced at low Mg concentrations when Mn2+ is also present. After stimulating the initial reaction rate, ethanol causes a rapid decrease in the rate of the Mg2+-activated reaction during incubation at 20 degrees C. At 27 degrees C, all surface-active compounds inhibit the Mg2+-activated reaction. Preincubation of the enzyme at 30 degrees C or below with DNA template and divalent cation increases the initial reaction rate, suggesting that formation of an enzyme-divalent cation-DNA template complex occurs as the first step in DNA polymerase III catalysis. The apparent Km at 21 degrees C for gapped calf thymus DNA was 25 muM with Mn2+ and 125 muM with Mg2+ for DNA polymerase III, and 18 muM at 30 degrees C for DNA polymerase II with either Mn2+ or Mg2+. Reactions with poly[d(A-T)] were enhanced by Mn2+ relative to Mg2+, and activity with poly(rA)-poly(dT) was Mn2+ dependent for both enzymes.
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31
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Travaglini EC, Dube DK, Surrey S, Loeb LA. Template recognition and chain elongation in DNA synthesis in vitro. J Mol Biol 1976; 106:605-21. [PMID: 185394 DOI: 10.1016/0022-2836(76)90254-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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32
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Modak MJ. A simplified procedure for the quantitative isolation of DNA and RNA transcripts synthesized in vitro. Anal Biochem 1976; 75:340-4. [PMID: 60891 DOI: 10.1016/0003-2697(76)90087-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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33
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Houdebine LM. Synthesis of DNA complementary to the mRNAs for milk proteins by E. coli DNA polymerase I. Nucleic Acids Res 1976; 3:615-30. [PMID: 775441 PMCID: PMC342928 DOI: 10.1093/nar/3.3.615] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
E.Coli DNA polymerase I (Klenow subfragment) was used for the synthesis of complementary DNA with the mRNAs for rabbit milk proteins as templates. The cDNA formed, contained 200 nucleotides and represented about 20% of the mRNA template. The cDNA was hybridized specifically to the mRNA templates. The Klenow subfragment of the E.Coli DNA polymerase I was as efficient as the avian myeloblastosis virus reverse transcriptase in the synthesis of cDNA. The mean size of the cDNA fragments obtained with the Klenow enzyme proved to be 70% of the value obtained with the AMV reverse transcriptase and at least twice the value generally obtained with the complete E.Coli DNA polymerase I. The cDNA was used for the detection and the quantification of the mRNA template in various RNA fractions.
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34
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Daubert S, Dahmus ME. Synthesis and characterization of a DNA probe complementary to rat liver 28S ribosomal RNA. Biochem Biophys Res Commun 1976; 68:1037-44. [PMID: 57777 DOI: 10.1016/0006-291x(76)90300-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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35
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On the fidelity of DNA replication. Enzyme activities associated with DNA polymerases from RNA tumor viruses. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(17)33788-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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36
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Lieberman MW. Approaches to the analysis of fidelity of DNA repair in mammalian cells. INTERNATIONAL REVIEW OF CYTOLOGY 1976; 45:1-23. [PMID: 783064 DOI: 10.1016/s0074-7696(08)60076-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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37
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38
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39
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Travaglini EC, Mildvan AS, Loeb LA. Kinetic analysis of Escherichia coli deoxyribonucleic acid polymerase I. J Biol Chem 1975. [DOI: 10.1016/s0021-9258(19)40720-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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40
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41
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Gillespie D, Saxinger WC, Gallo RC. Information transfer in cells infected by RNA tumor viruses and extension to human neoplasia. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1975; 15:1-108. [PMID: 49067 DOI: 10.1016/s0079-6603(08)60117-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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42
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Poiesz BJ, Seal G, Loeb LA. Reverse transcriptase: correlation of zinc content with activity. Proc Natl Acad Sci U S A 1974; 71:4892-6. [PMID: 4140513 PMCID: PMC434005 DOI: 10.1073/pnas.71.12.4892] [Citation(s) in RCA: 43] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Evidence is presented that DNA polymerase of avian myeloblastosis virus has an obligatory zinc requirement for activity. Previous studies indicate that the purified polymerase contains zinc in a stoichiometry of about 1 g-atom/mole. We now find that the enzyme-bound zinc is exchangeable with radioactive (65)Zn; after isoelectric focusing, the radioactive (65)Zn is coincident with polymerase activity. Dialysis of the (65)Zn-labeled polymerase against the chelator, 1,10-phenanthroline, results in a progressive loss of radioactive (65)Zn and polymerase activity. Thereupon, incubation of the inactivated enzyme with Zn(2+) fully restores activity. Thus, the DNA polymerase present in an oncogenic RNA virus, like animal DNA polymerases, can be rigorously classified as a zinc metalloenzyme. DNA polymerase of avian myeloblastosis virus is inactivated by 1,10-phenanthroline at a much faster rate than the bacterial and animal DNA polymerases that have been tested. It may, therefore, be possible to inactivate selectively DNA polymerases from animal tumor viruses by brief exposure to appropriate metal chelators.
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43
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Nemer M, Graham M, Dubroff LM. Co-existence of non-histone messenger RNA species lacking and containing polyadenylic acid in sea urchin embryos. J Mol Biol 1974; 89:435-54. [PMID: 4444055 DOI: 10.1016/0022-2836(74)90474-4] [Citation(s) in RCA: 128] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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44
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Modak MJ, Marcus SL, Cavalieri LF. A New Sensitive Method for Detecting Polyadenylate in Viral and Other Ribonucleic Acids Using Escherichia coli Deoxyribonucleic Acid Polymerase I. J Biol Chem 1974. [DOI: 10.1016/s0021-9258(19)42113-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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45
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Wickremasinghe RG, Johnston IR. Evidence that the DNA- and poly(A)-dependent DNA polymerase activities of rat liver nuclei are functions of the same enzyme. Some observations on its mode of action. BIOCHIMICA ET BIOPHYSICA ACTA 1974; 361:37-52. [PMID: 4282026 DOI: 10.1016/0005-2787(74)90207-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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46
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Beljanski M, Beljanski M. RNA-bound reverse transcriptase in Escherichia coli and in vitro synthesis of a complementary DNA. Biochem Genet 1974; 12:163-80. [PMID: 4138163 DOI: 10.1007/bf00487823] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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47
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Sarin PS, Reitz MS, Gallo RC. Transcription of heteropolymeric regions of avian myeloblastosis virus high molecular weight RNA with Escherichia coli DNA polymerase I. Biochem Biophys Res Commun 1974; 59:202-14. [PMID: 4135407 DOI: 10.1016/s0006-291x(74)80194-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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48
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Gulati SC, Kacian DL, Spiegelman S. Conditions for using DNA polymerase I as an RNA-dependent DNA polymerase. Proc Natl Acad Sci U S A 1974; 71:1035-9. [PMID: 4133845 PMCID: PMC388156 DOI: 10.1073/pnas.71.4.1035] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Conditions are described for using Escherichia coli DNA polymerase I for synthesizing complementary DNA copies of natural RNA molecules, which are suitable for use in hybridization experiments. The molar ratio of enzyme to template is critical; below a certain level, synthesis is not observed. Hybrids formed with the complementary DNA are of comparable specificity and stability to those formed with complementary DNAs synthesized by viral RNA-directed DNA polymerase. Synthesis of dA-dT polymers, a common occurrence with this enzyme, can be eliminated by including distamycin in the reaction mixture.
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49
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RNA-Directed DNA Polymerase—Properties and Functions in Oncogenic RNA Viruses and Cells1. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/s0079-6603(08)60208-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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50
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Loeb LA. 6. Eucaryotic DNA Polymerases. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/s1874-6047(08)60138-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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