Reverse transcriptase - wikipedia Reverse transcriptase Reverse transcriptase ( RNA - dependent DNA polymerase ) Crystallographic structure of HIV - 1 reverse transcriptase where the two subunits p51 and p66 are colored and the active sites of polymerase and nuclease are highlighted. Identifiers Symbol RVT_1 Pfam PF00078 Pfam clan CL0027 InterPro IPR000477 PROSITE PS50878 SCOP 1hmv SUPERFAMILY 1hmv CDD cd00304 Available protein structures : Pfam structures PDB RCSB PDB ; PDBe ; PDBj PDBsum structure summary RNA - directed DNA polymerase Identifiers EC number 2.7. 7.49 CAS number 9068 - 38 - 6 Databases IntEnz IntEnz view BRENDA BRENDA entry ExPASy NiceZyme view KEGG KEGG entry MetaCyc metabolic pathway PRIAM profile PDB structures RCSB PDB PDBe PDBsum Gene Ontology AmiGO / QuickGO Search PMC articles PubMed articles NCBI proteins A reverse transcriptase ( RT ) is an enzyme used to generate complementary DNA ( cDNA ) from an RNA template, a process termed reverse transcription. It is mainly associated with retroviruses. However, non-retroviruses also use RT ( for example, the hepatitis B virus, a member of the Hepadnaviridae, which are dsDNA - RT viruses, while retroviruses are ssRNA viruses ). RT inhibitors are widely used as antiretroviral drugs. RT activities are also associated with the replication of chromosome ends ( telomerase ) and some mobile genetic elements ( retrotransposons ). Retroviral RT has three sequential biochemical activities : ( a ) RNA - dependent DNA polymerase activity, ( b ) ribonuclease H, and ( c ) DNA - dependent DNA polymerase activity. These activities are used by the retrovirus to convert single - stranded genomic RNA into double - stranded cDNA which can integrate into the host genome, potentially generating a long - term infection that can be very difficult to eradicate. The same sequence of reactions is widely used in the laboratory to convert RNA to DNA for use in molecular cloning, RNA sequencing, polymerase chain reaction ( PCR ), or genome analysis. Well studied reverse transcriptases include : HIV - 1 reverse transcriptase from human immunodeficiency virus type 1 ( PDB : 1HMV ​ ) has two subunits, which have respective molecular weights of 66 and 51 kDa. M - MLV reverse transcriptase from the Moloney murine leukemia virus is a single 75 kDa monomer. AMV reverse transcriptase from the avian myeloblastosis virus also has two subunits, a 63 kDa subunit and a 95 kDa subunit. Telomerase reverse transcriptase that maintains the telomeres of eukaryotic chromosomes. Contents 1 History 2 Function in viruses 2.1 Process of reverse transcription 2.1. 1 Retroviral reverse transcription 3 In eukaryotes 4 In prokaryotes 5 Evolutionary role 6 Structure 7 Replication fidelity 8 Applications 8.1 Antiviral drugs 8.2 Molecular biology 9 See also 10 References 11 External links History Reverse transcriptases were discovered by Howard Temin at the University of Wisconsin -- Madison in RSV virions and independently isolated by David Baltimore in 1970 at MIT from two RNA tumour viruses : R - MLV and again RSV. For their achievements, both shared the 1975 Nobel Prize in Physiology or Medicine ( with Renato Dulbecco ). The idea of reverse transcription was very unpopular at first, as it contradicted the central dogma of molecular biology, which states that DNA is transcribed into RNA, which is then translated into proteins. However, in 1970, when the scientists Howard Temin and David Baltimore both independently discovered the enzyme responsible for reverse transcription, named reverse transcriptase, the possibility that genetic information could be passed on in this manner was finally accepted. Function in viruses Reverse transcriptase is shown with its finger, palm, and thumb regions. The catalytic amino acids of the RNase H active site and the polymerase active site are shown in ball - and - stick form. The enzymes are encoded and used by viruses that use reverse transcription as a step in the process of replication. Reverse - transcribing RNA viruses, such as retroviruses, use the enzyme to reverse - transcribe their RNA genomes into DNA, which is then integrated into the host genome and replicated along with it. Reverse - transcribing DNA viruses, such as the hepadnaviruses, can allow RNA to serve as a template in assembling and making DNA strands. HIV infects humans with the use of this enzyme. Without reverse transcriptase, the viral genome would not be able to incorporate into the host cell, resulting in failure to replicate. Process of reverse transcription Reverse transcriptase creates double - stranded DNA from an RNA template. In virus species with reverse transcriptase lacking DNA - dependent DNA polymerase activity, creation of double - stranded DNA can possibly be done by host - encoded DNA polymerase δ, mistaking the viral DNA - RNA for a primer and synthesizing a double - stranded DNA by similar mechanism as in primer removal, where the newly synthesized DNA displaces the original RNA template. The process of reverse transcription is extremely error - prone, and it is during this step that mutations may occur. Such mutations may cause drug resistance. Retroviral reverse transcription Retroviruses, also referred to as class VI ssRNA - RT viruses, are RNA reverse - transcribing viruses with a DNA intermediate. Their genomes consist of two molecules of positive - sense single - stranded RNA with a 5 ' cap and 3 ' polyadenylated tail. Examples of retroviruses include the human immunodeficiency virus ( HIV ) and the human T - lymphotropic virus ( HTLV ). Creation of double - stranded DNA occurs in the cytosol as a series of these steps : Lysyl tRNA acts as a primer and hybridizes to a complementary part of the virus RNA genome called the primer binding site or PBS. Reverse transcriptase then adds DNA nucleotides onto the 3 ' end of the primer, synthesizing DNA complementary to the U5 ( non-coding region ) and R region ( a direct repeat found at both ends of the RNA molecule ) of the viral RNA. A domain on the reverse transcriptase enzyme called RNAse H degrades the U5 and R regions on the 5 ' end of the RNA. The primer then `` jumps '' to the 3 ' end of the viral genome, and the newly synthesised DNA strands hybridizes to the complementary R region on the RNA. The complementary DNA ( cDNA ) added in ( 2 ) is further extended, and then the majority of viral RNA is degraded by RNAse H, leaving only the PP sequence. Synthesis of the second DNA strand begins, using the remaining fragment of viral RNA as a primer. There is then another `` jump '' where the PBS from the second strand hybridizes with the complementary PBS on the first strand. Both strands are extended to form a complete double - stranded DNA copy of the original viral RNA genome, which can then be incorporated into the host 's genome by the enzyme integrase. Creation of double - stranded DNA also involves strand transfer, in which there is a translocation of short DNA product from initial RNA - dependent DNA synthesis to acceptor template regions at the other end of the genome, which are later reached and processed by the reverse transcriptase for its DNA - dependent DNA activity. Retroviral RNA is arranged in 5 ' terminus to 3 ' terminus. The site where the primer is annealed to viral RNA is called the primer - binding site ( PBS ). The RNA 5'end to the PBS site is called U5, and the RNA 3 ' end to the PBS is called the leader. The tRNA primer is unwound between 14 and 22 nucleotides and forms a base - paired duplex with the viral RNA at PBS. The fact that the PBS is located near the 5 ' terminus of viral RNA is unusual because reverse transcriptase synthesize DNA from 3 ' end of the primer in the 5 ' to 3 ' direction ( with respect to the RNA template ). Therefore, the primer and reverse transcriptase must be relocated to 3 ' end of viral RNA. In order to accomplish this reposition, multiple steps and various enzymes including DNA polymerase, ribonuclease H ( RNase H ) and polynucleotide unwinding are needed. The HIV reverse transcriptase also has ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA - dependent DNA polymerase activity that copies the sense cDNA strand into an antisense DNA to form a double - stranded viral DNA intermediate ( vDNA ). In eukaryotes Self - replicating stretches of eukaryotic genomes known as retrotransposons utilize reverse transcriptase to move from one position in the genome to another via an RNA intermediate. They are found abundantly in the genomes of plants and animals. Telomerase is another reverse transcriptase found in many eukaryotes, including humans, which carries its own RNA template ; this RNA is used as a template for DNA replication. In prokaryotes Initial reports of reverse transcriptase in prokaryotes came as far back as 1971 ( Beljanski et al., 1971a, 1972 ). These have since been broadly described as part of bacterial Retrons, distinct sequences that code for reverse transcriptase, and are used in the synthesis of msDNA. In order to initiate synthesis of DNA, a primer is needed. In bacteria, the primer is synthesized during replication. Evolutionary role Valerian Dolja of Oregon State argues that viruses, due to their diversity, have played an evolutionary role in the development of cellular life, with reverse transcriptase playing a central role. Structure Reverse transcriptase enzymes include an RNA - dependent DNA polymerase and a DNA - dependent DNA polymerase, which work together to perform reverse transcription. In addition to the transcription function, retroviral reverse transcriptases have a domain belonging to the RNase H family, which is vital to their replication. Replication fidelity There are three different replication systems during the life cycle of a retrovirus. First of all, the reverse transcriptase synthesizes viral DNA from viral RNA, and then from newly made complementary DNA strand. The second replication process occurs when host cellular DNA polymerase replicates the integrated viral DNA. Lastly, RNA polymerase II transcribes the proviral DNA into RNA, which will be packed into virions. Therefore, mutation can occur during one or all of these replication steps. Reverse transcriptase has a high error rate when transcribing RNA into DNA since, unlike most other DNA polymerases, it has no proofreading ability. This high error rate allows mutations to accumulate at an accelerated rate relative to proofread forms of replication. The commercially available reverse transcriptases produced by Promega are quoted by their manuals as having error rates in the range of 1 in 17,000 bases for AMV and 1 in 30,000 bases for M - MLV. Other than creating single - nucleotide polymorphisms, reverse transcriptases have also been shown to be involved in processes such as transcript fusions, exon shuffling and creating artificial antisense transcripts. It has been speculated that this template switching activity of reverse transcriptase, which can be demonstrated completely in vivo, may have been one of the causes for finding several thousand unannotated transcripts in the genomes of model organisms. Applications The molecular structure of zidovudine ( AZT ), a drug used to inhibit HIV reverse transcriptase Antiviral drugs Further information : Reverse - transcriptase inhibitor As HIV uses reverse transcriptase to copy its genetic material and generate new viruses ( part of a retrovirus proliferation circle ), specific drugs have been designed to disrupt the process and thereby suppress its growth. Collectively, these drugs are known as reverse - transcriptase inhibitors and include the nucleoside and nucleotide analogues zidovudine ( trade name Retrovir ), lamivudine ( Epivir ) and tenofovir ( Viread ), as well as non-nucleoside inhibitors, such as nevirapine ( Viramune ). Molecular biology Further information : Reverse transcription polymerase chain reaction Reverse transcriptase is commonly used in research to apply the polymerase chain reaction technique to RNA in a technique called reverse transcription polymerase chain reaction ( RT - PCR ). The classical PCR technique can be applied only to DNA strands, but, with the help of reverse transcriptase, RNA can be transcribed into DNA, thus making PCR analysis of RNA molecules possible. Reverse transcriptase is used also to create cDNA libraries from mRNA. The commercial availability of reverse transcriptase greatly improved knowledge in the area of molecular biology, as, along with other enzymes, it allowed scientists to clone, sequence, and characterise RNA. Reverse transcriptase has also been employed in insulin production. By inserting eukaryotic mRNA for insulin production along with reverse transcriptase into bacteria, the mRNA could be inserted into the prokaryote 's genome. Large amounts of insulin can then be created, sidestepping the need to harvest pig pancreas and other such traditional sources. Directly inserting eukaryotic DNA into bacteria would not work because it carries introns, so would not translate successfully using the bacterial ribosomes. Processing in the eukaryotic cell during mRNA production removes these introns to provide a suitable template. Reverse transcriptase converted this edited RNA back into DNA so it could be incorporated in the genome. See also Molecular and cellular biology portal Viruses portal cDNA library DNA polymerase msDNA Reverse transcribing virus RNA polymerase Telomerase Retrotransposon marker References Jump up ^ PDB : 3KLF ​ ; Tu X, Das K, Han Q, Bauman JD, Clark AD, Hou X, Frenkel YV, Gaffney BL, Jones RA, Boyer PL, Hughes SH, Sarafianos SG, Arnold E ( September 2010 ). `` Structural basis of HIV - 1 resistance to AZT by excision ''. Nat. Struct. Mol. Biol. 17 ( 10 ) : 1202 -- 9. doi : 10.1038 / nsmb. 1908. PMC 2987654. PMID 20852643. Jump up ^ Ferris, AL ; Hizi, A ; Showalter, SD ; Pichuantes, S ; Babe, L ; Craik, CS ; Hughes, SH ( April 1990 ). `` Immunologic and proteolytic analysis of HIV - 1 reverse transcriptase structure '' ( PDF ). Virology. 175 ( 2 ) : 456 -- 64. doi : 10.1016 / 0042 - 6822 ( 90 ) 90430 - y. PMID 1691562. ^ Jump up to : Konishi A, Yasukawa K, Inouye K ( 2012 ). `` Improving the thermal stability of avian myeloblastosis virus reverse transcriptase α - subunit by site - directed mutagenesis '' ( PDF ). Biotechnol. Lett. 34 ( 7 ) : 1209 -- 15. doi : 10.1007 / s10529 - 012 - 0904 - 9. PMID 22426840. Jump up ^ Temin HM, Mizutani S ( June 1970 ). `` RNA - dependent DNA polymerase in virions of Rous sarcoma virus ''. Nature. 226 ( 5252 ) : 1211 -- 3. doi : 10.1038 / 2261211a0. PMID 4316301. Jump up ^ Baltimore D. ( June 1970 ). `` RNA - dependent DNA polymerase in virions of RNA tumour viruses ''. Nature. 226 ( 5252 ) : 1209 -- 11. doi : 10.1038 / 2261209a0. PMID 4316300. Jump up ^ `` Central dogma reversed ''. Nature. 226 ( 5252 ) : 1198 -- 9. June 1970. doi : 10.1038 / 2261198a0. PMID 5422595. Jump up ^ Bio-Medicine.org - Retrovirus Retrieved on 17 Feb, 2009 Jump up ^ Telesnitsky A, Goff SP ( 1993 ). `` Strong - stop strand transfer during reverse transcription ''. In Skalka MA, Goff SP. Reverse transcriptase ( 1st ed. ). New York : Cold Spring Harbor. p. 49. ISBN 0 - 87969 - 382 - 7. Jump up ^ Bernstein A, Weiss R, Tooze J ( 1985 ). `` RNA tumor viruses ''. Molecular Biology of Tumor Viruses ( 2nd ed. ). Cold Spring Harbor, N.Y. : Cold Spring Harbor Laboratory. Jump up ^ Moelling, Karin ; Broecker, Felix ( 2015 ). `` The reverse transcriptase - RNase H : from viruses to antiviral defense ''. Annals of the New York Academy of Sciences. 1341 ( 1 ) : 126 -- 135. doi : 10.1111 / nyas. 12668. ISSN 0077 - 8923. Jump up ^ Doc Kaiser 's Microbiology Home Page > IV. VIRUSES > F. ANIMAL VIRUS LIFE CYCLES > 3. The Life Cycle of HIV Archived 2010 - 07 - 26 at the Wayback Machine. Community College of Baltimore County. Updated : Jan 2008. Jump up ^ Krieger M, Scott MP, Matsudaira PT, Lodish HF, Darnell JE, Zipursky L, Kaiser C, Berk A ( 2004 ). Molecular cell biology. New York : W.H. Freeman and CO. ISBN 0 - 7167 - 4366 - 3. Jump up ^ Hurwitz J, Leis JP ( January 1972 ). `` RNA - dependent DNA polymerase activity of RNA tumor viruses. I. Directing influence of DNA in the reaction ''. J. Virol. 9 ( 1 ) : 116 -- 29. PMC 356270. PMID 4333538. Jump up ^ Arnold, Carrie ( 17 July 2014 ). `` Could Giant Viruses Be the Origin of Life on Earth ? ''. news.nationalgeographic.com. Retrieved 29 May 2016. Jump up ^ Bbenek K, Kunkel AT ( 1993 ). `` The fidelity of retroviral reverse transcriptases ''. In Skalka MA, Goff PS. Reverse transcriptase. New York : Cold Spring Harbor Laboratory Press. p. 85. ISBN 0 - 87969 - 382 - 7. Jump up ^ Promega kit instruction manual ( 1999 ) Archived 2006 - 11 - 21 at the Wayback Machine. Jump up ^ Houseley J, Tollervey D ( 2010 ). `` Apparent non-canonical trans - splicing is generated by reverse transcriptase in vitro ''. PLoS ONE. 5 ( 8 ) : e12271. doi : 10.1371 / journal. pone. 0012271. PMC 2923612. PMID 20805885. Jump up ^ Zeng XC, Wang SX ( June 2002 ). `` Evidence that BmTXK beta - BmKCT cDNA from Chinese scorpion Buthus martensii Karsch is an artifact generated in the reverse transcription process ''. FEBS Lett. 520 ( 1 -- 3 ) : 183 -- 4 ; author reply 185. doi : 10.1016 / S0014 - 5793 ( 02 ) 02812 - 0. PMID 12044895. Jump up ^ van Bakel H, Nislow C, Blencowe BJ, Hughes TR ( 2011 ). `` Response to `` The Reality of Pervasive Transcription '' ``. PLoS Biology. 9 ( 7 ) : e1001102. doi : 10.1371 / journal. pbio. 1001102. External links RNA Transcriptase at the US National Library of Medicine Medical Subject Headings ( MeSH ) animation of reverse transcriptase action and three reverse transcriptase inhibitors Molecule of the month ( September 2002 ) at the RCSB PDB HIV Replication 3D Medical Animation. ( Nov 2008 ). Video by Boehringer Ingelheim. Goodsell DS. `` Molecule of the Month : Reverse Transcriptase ( Sep 2002 ) ''. Research Collaboratory for Structural Bioinformatics ( RCSB ) Protein Data Bank ( PDB ). Retrieved 2013 - 01 - 13. Viral proteins ( early and late ) DNA Herpes simplex Herpes simplex virus protein vmw65 HHV capsid portal protein Hepatitis B HBsAg HBcAg HBeAg HBx Hepatitis B virus DNA polymerase Epstein -- Barr EBNA - 1 EBNA - 2 EBNA - 3 LMP - 1 LMP - 2 EBER RNA Rotavirus VNPs : NSP1 NSP2 NSP4 NSP5 NSP6 Influenza capsid : matrix protein M1 protein viral envelope M2 protein glycoprotein : Influenza hemagglutinin Neuraminidase Parainfluenza Parainfluenza hemagglutinin - neuraminidase Mumps Mumps hemagglutinin - neuraminidase Measles Measles hemagglutinin RSV Respiratory syncytial virus G protein Hepatitis C VSPs : E1 E2 VNPs : P7 NS2 NS3 NS4A NS4B NS5A NS5B RT Structure and genome of HIV VSPs : gag pol Integrase Reverse transcriptase HIV - 1 protease env gp120 gp41 VRAPs : transactivators Tat Rev Vpr Nef Vif Vpu Fusion protein Gag - onc fusion protein Other B13R Transferases : phosphorus - containing groups ( EC 2.7 ) 2.7. 1 - 2.7. 4 : phosphotransferase / kinase ( PO ) 2.7. 1 : OH acceptor Hexo - Gluco - Fructo - Hepatic Galacto - Phosphofructo - Liver Muscle Platelet Riboflavin Shikimate Thymidine ADP - thymidine NAD Glycerol Pantothenate Mevalonate Pyruvate Deoxycytidine PFP Diacylglycerol Phosphoinositide 3 Class I PI 3 Class II PI 3 Sphingosine Glucose - 1, 6 - bisphosphate synthase 2.7. 2 : COOH acceptor Phosphoglycerate Aspartate kinase 2.7. 3 : N acceptor Creatine 2.7. 4 : PO acceptor Phosphomevalonate Adenylate Nucleoside - diphosphate Uridylate Guanylate Thiamine - diphosphate 2.7. 6 : diphosphotransferase ( P O ) Ribose - phosphate diphosphokinase Thiamine diphosphokinase 2.7. 7 : nucleotidyltransferase ( PO - nucleoside ) Polymerase DNA polymerase DNA - directed DNA polymerase II III IV V RNA - directed DNA polymerase Reverse transcriptase Telomerase DNA nucleotidylexotransferase / Terminal deoxynucleotidyl transferase RNA nucleotidyltransferase RNA polymerase / DNA - directed RNA polymerase RNA polymerase I II III IV V Primase RNA - dependent RNA polymerase PNPase Phosphorolytic 3 ' to 5 ' exoribonuclease RNase PH PNPase Nucleotidyltransferase UTP -- glucose - 1 - phosphate uridylyltransferase Galactose - 1 - phosphate uridylyltransferase Guanylyltransferase mRNA capping enzyme Other Recombinase ( Integrase ) Transposase 2.7. 8 : miscellaneous Phosphatidyltransferases CDP - diacylglycerol -- glycerol - 3 - phosphate 3 - phosphatidyltransferase CDP - diacylglycerol -- serine O - phosphatidyltransferase CDP - diacylglycerol -- inositol 3 - phosphatidyltransferase CDP - diacylglycerol -- choline O - phosphatidyltransferase Glycosyl - 1 - phosphotransferase N - acetylglucosamine - 1 - phosphate transferase 2.7. 10 - 2.7. 13 : protein kinase ( PO ; protein acceptor ) 2.7. 10 : protein - tyrosine see tyrosine kinases 2.7. 11 : protein - serine / threonine see serine / threonine - specific protein kinases 2.7. 12 : protein - dual - specificity see serine / threonine - specific protein kinases 2.7. 13 : protein - histidine Protein - histidine pros - kinase Protein - histidine tele - kinase Histidine kinase Retrieved from `` https://en.wikipedia.org/w/index.php?title=Reverse_transcriptase&oldid=837433469 '' Categories : Genetics EC 2.7. 7 Molecular biology Viral enzymes Telomeres Hidden categories : Webarchive template wayback links Talk Search Contents About Wikipedia Bosanski Català Čeština Dansk Deutsch Eesti Ελληνικά Español Euskara فارسی Français Galego 한국어 Bahasa Indonesia Italiano עברית ქართული Қазақша Lietuvių Luganda Magyar Nederlands 日本 語 Occitan Polski Português Русский Simple English Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska ไทย Türkçe Українська اردو Tiếng Việt 中文 31 more Edit links This page was last edited on 20 April 2018, at 19 : 56. 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Question: what is the role of reverse transcriptase in retroviral infection
Answer: to convert single-stranded genomic RNA into double-stranded cDNA which can integrate into the host genome, potentially generating a long-term infection that can be very difficult to eradicate