Genomic flexibility of human endogenous retrovirus type K
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POSTER PRESENTATION Open Access Genomic flexibility of human endogenous retrovirus type K Derek Dube * , Rafael Contreras-Galindo, Shirley He, Steven King, Marta Gonzalez-Hernandez, Scott Gitlin, Mark Kaplan, David Markovitz From Frontiers of Retrovirology: Complex retroviruses, retroelements and their hosts Cambridge, UK. 16-18 September 2013 Background Human Endogenous Retrovirus Type K (HML-2), HERV-K, is the most recent group of retroviral pro- viruses to enter the human genome. In several cases, these HERV-K proviruses have maintained their geno- mic structure and relevant coding regions relatively unperturbed by the mutations that have inactivated other endogenous viral elements. While no infectious HERV-K virus has been detected to date, resuscitation of infectious clones, derived from consensus sequences of selected HERV-K proviruses, has allowed the histori- cal HERV-K replication cycle to be examined for the first time. Traditionally, it has been thought that HERV- K viruses replicated in a manner similar to canonical retroviruses; that is, with reverse transcription following the entry of an infectious virus particle into a permissive host cell. Here, we provide evidence that, historically, HERV-K viruses may have utilized an additional mechanism for replication, reverse transcribing the RNA genome into DNA prior to viral release from the host cell. Materials and methods HERV-K viral samples were collected from teratocar- cinoma cell lines and plasma of patients with lym- phoma. HERV-K viral loads were determined by quantitative RT-PCR and PCR, after employing speci- fic DNase and enzyme-treatment procedures to differ- entiate genomic type (RNA and DNA). Additionally, HERV-KCON [1] and control viruses (MLV and HIV), were produced in the presence or absence of reverse transcriptase inhibitors (RTIs) to examine the infectiv- ity of these viruses. Results HERV-K DNA genomes, in addition to the expected HERV-K RNA genomes, were detected within extracel- lular HERV-K viral particles from both HERV-K produ- cing cell lines and lymphoma patient plasma, even after the removal of extra-viral contaminating DNAs by DNase-treatment prior to viral lysis. Further, these DNA genomes were determined to represent newly reverse transcribed DNA (RT-DNA), and could be eliminated by culturing the HERV-K producing cell lines in the presence of RTIs. Additionally, using the resuscitated HERV-KCON virus, we found that both HERV-K parti- cles containing RNA genomes and particles containing DNA genomes are capable of infecting target cells. This differs from the canonical retroviruses tested, MLV and HIV, in which infectivity was seen exclusively from viruses with RNA genomes. Conclusions Our data suggest that, both historically and currently, HERV-K virus populations include both RNA and DNA containing particles. This genomic flexibility represents a previously undescribed mechanism of viral replication, and historically would have permitted these viruses to replicate in variable host cell environ- ments, potentially assisting in their many integration events and resulting in their high prevalence within the human genome. Moreover, the ability of modern HERV-K viruses to proceed through reverse transcrip- tion and package RT-DNA genomes suggests a higher level of replication competency than previously under- stood, and may be relevant in current HERV-K-associated diseases. Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA Dube et al. Retrovirology 2013, 10(Suppl 1):P29 http://www.retrovirology.com/content/10/S1/P29 © 2013 Dube et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Transcript of Genomic flexibility of human endogenous retrovirus type K
POSTER PRESENTATION Open Access
Genomic flexibility of human endogenousretrovirus type KDerek Dube*, Rafael Contreras-Galindo, Shirley He, Steven King, Marta Gonzalez-Hernandez, Scott Gitlin,Mark Kaplan, David Markovitz
From Frontiers of Retrovirology: Complex retroviruses, retroelements and their hostsCambridge, UK. 16-18 September 2013
BackgroundHuman Endogenous Retrovirus Type K (HML-2),HERV-K, is the most recent group of retroviral pro-viruses to enter the human genome. In several cases,these HERV-K proviruses have maintained their geno-mic structure and relevant coding regions relativelyunperturbed by the mutations that have inactivatedother endogenous viral elements. While no infectiousHERV-K virus has been detected to date, resuscitationof infectious clones, derived from consensus sequencesof selected HERV-K proviruses, has allowed the histori-cal HERV-K replication cycle to be examined for thefirst time. Traditionally, it has been thought that HERV-K viruses replicated in a manner similar to canonicalretroviruses; that is, with reverse transcription followingthe entry of an infectious virus particle into a permissivehost cell. Here, we provide evidence that, historically,HERV-K viruses may have utilized an additionalmechanism for replication, reverse transcribing theRNA genome into DNA prior to viral release from thehost cell.
Materials and methodsHERV-K viral samples were collected from teratocar-cinoma cell lines and plasma of patients with lym-phoma. HERV-K viral loads were determined byquantitative RT-PCR and PCR, after employing speci-fic DNase and enzyme-treatment procedures to differ-entiate genomic type (RNA and DNA). Additionally,HERV-KCON [1] and control viruses (MLV and HIV),were produced in the presence or absence of reversetranscriptase inhibitors (RTIs) to examine the infectiv-ity of these viruses.
ResultsHERV-K DNA genomes, in addition to the expectedHERV-K RNA genomes, were detected within extracel-lular HERV-K viral particles from both HERV-K produ-cing cell lines and lymphoma patient plasma, even afterthe removal of extra-viral contaminating DNAs byDNase-treatment prior to viral lysis. Further, these DNAgenomes were determined to represent newly reversetranscribed DNA (RT-DNA), and could be eliminatedby culturing the HERV-K producing cell lines in thepresence of RTIs. Additionally, using the resuscitatedHERV-KCON virus, we found that both HERV-K parti-cles containing RNA genomes and particles containingDNA genomes are capable of infecting target cells. Thisdiffers from the canonical retroviruses tested, MLV andHIV, in which infectivity was seen exclusively fromviruses with RNA genomes.
ConclusionsOur data suggest that, both historically and currently,HERV-K virus populations include both RNA andDNA containing particles. This genomic flexibilityrepresents a previously undescribed mechanism of viralreplication, and historically would have permittedthese viruses to replicate in variable host cell environ-ments, potentially assisting in their many integrationevents and resulting in their high prevalence withinthe human genome. Moreover, the ability of modernHERV-K viruses to proceed through reverse transcrip-tion and package RT-DNA genomes suggests a higherlevel of replication competency than previously under-stood, and may be relevant in current HERV-K-associateddiseases.
Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
Dube et al. Retrovirology 2013, 10(Suppl 1):P29http://www.retrovirology.com/content/10/S1/P29
© 2013 Dube et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative CommonsAttribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction inany medium, provided the original work is properly cited.
Published: 19 September 2013
Reference1. Lee YN, Bieniasz PD: Reconstitution of an infectious human endogenous
retrovirus. PLoS Pathog 2007, 3:e10.
doi:10.1186/1742-4690-10-S1-P29Cite this article as: Dube et al.: Genomic flexibility of humanendogenous retrovirus type K. Retrovirology 2013 10(Suppl 1):P29.
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