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Ramic M, Andrade NS, Rybin MJ, Esanov R, Wahlestedt C, Benatar M, Zeier Z. Epigenetic Small Molecules Rescue Nucleocytoplasmic Transport and DNA Damage Phenotypes in C9ORF72 ALS/FTD. Brain Sci 2021; 11:brainsci11111543. [PMID: 34827542 PMCID: PMC8616043 DOI: 10.3390/brainsci11111543] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 11/11/2021] [Accepted: 11/18/2021] [Indexed: 01/04/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease with available treatments only marginally slowing progression or improving survival. A hexanucleotide repeat expansion mutation in the C9ORF72 gene is the most commonly known genetic cause of both sporadic and familial cases of ALS and frontotemporal dementia (FTD). The C9ORF72 expansion mutation produces five dipeptide repeat proteins (DPRs), and while the mechanistic determinants of DPR-mediated neurotoxicity remain incompletely understood, evidence suggests that disruption of nucleocytoplasmic transport and increased DNA damage contributes to pathology. Therefore, characterizing these disturbances and determining the relative contribution of different DPRs is needed to facilitate the development of novel therapeutics for C9ALS/FTD. To this end, we generated a series of nucleocytoplasmic transport “biosensors”, composed of the green fluorescent protein (GFP), fused to different classes of nuclear localization signals (NLSs) and nuclear export signals (NESs). Using these biosensors in conjunction with automated microscopy, we investigated the role of the three most neurotoxic DPRs (PR, GR, and GA) on seven nuclear import and two export pathways. In addition to other DPRs, we found that PR had pronounced inhibitory effects on the classical nuclear export pathway and several nuclear import pathways. To identify compounds capable of counteracting the effects of PR on nucleocytoplasmic transport, we developed a nucleocytoplasmic transport assay and screened several commercially available compound libraries, totaling 2714 compounds. In addition to restoring nucleocytoplasmic transport efficiencies, hits from the screen also counteract the cytotoxic effects of PR. Selected hits were subsequently tested for their ability to rescue another C9ALS/FTD phenotype—persistent DNA double strand breakage. Overall, we found that DPRs disrupt multiple nucleocytoplasmic transport pathways and we identified small molecules that counteract these effects—resulting in increased viability of PR-expressing cells and decreased DNA damage markers in patient-derived motor neurons. Several HDAC inhibitors were validated as hits, supporting previous studies that show that HDAC inhibitors confer therapeutic effects in neurodegenerative models.
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Affiliation(s)
- Melina Ramic
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
| | - Nadja S. Andrade
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
| | - Matthew J. Rybin
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
| | - Rustam Esanov
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
| | - Claes Wahlestedt
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
| | - Michael Benatar
- Department of Neurology, University of Miami Miller School of Medicine, 1120 NW 14th St., Miami, FL 33136, USA;
| | - Zane Zeier
- Center for Therapeutic Innovation, Department of Psychiatry & Behavioral Sciences, University of Miami Miller School of Medicine, 1501 NW 10th Ave, Miami, FL 33136, USA; (M.R.); (N.S.A.); (M.J.R.); (R.E.); (C.W.)
- Correspondence: ; Tel.: +1-305-243-1367
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The Unique, the Known, and the Unknown of Spumaretrovirus Assembly. Viruses 2021; 13:v13010105. [PMID: 33451128 PMCID: PMC7828637 DOI: 10.3390/v13010105] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/08/2021] [Accepted: 01/10/2021] [Indexed: 12/22/2022] Open
Abstract
Within the family of Retroviridae, foamy viruses (FVs) are unique and unconventional with respect to many aspects in their molecular biology, including assembly and release of enveloped viral particles. Both components of the minimal assembly and release machinery, Gag and Env, display significant differences in their molecular structures and functions compared to the other retroviruses. This led to the placement of FVs into a separate subfamily, the Spumaretrovirinae. Here, we describe the molecular differences in FV Gag and Env, as well as Pol, which is translated as a separate protein and not in an orthoretroviral manner as a Gag-Pol fusion protein. This feature further complicates FV assembly since a specialized Pol encapsidation strategy via a tripartite Gag-genome–Pol complex is used. We try to relate the different features and specific interaction patterns of the FV Gag, Pol, and Env proteins in order to develop a comprehensive and dynamic picture of particle assembly and release, but also other features that are indirectly affected. Since FVs are at the root of the retrovirus tree, we aim at dissecting the unique/specialized features from those shared among the Spuma- and Orthoretrovirinae. Such analyses may shed light on the evolution and characteristics of virus envelopment since related viruses within the Ortervirales, for instance LTR retrotransposons, are characterized by different levels of envelopment, thus affecting the capacity for intercellular transmission.
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O'Carroll IP, Fan L, Kroupa T, McShane EK, Theodore C, Yates EA, Kondrup B, Ding J, Martin TS, Rein A, Wang YX. Structural Mimicry Drives HIV-1 Rev-Mediated HERV-K Expression. J Mol Biol 2020; 432:166711. [PMID: 33197463 DOI: 10.1016/j.jmb.2020.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 11/09/2020] [Accepted: 11/09/2020] [Indexed: 10/23/2022]
Abstract
Expression of the Human Endogenous Retrovirus Type K (HERV-K), the youngest and most active HERV, has been associated with various cancers and neurodegenerative diseases. As in all retroviruses, a fraction of HERV-K transcripts is exported from the nucleus in unspliced or incompletely spliced forms to serve as templates for translation of viral proteins. In a fraction of HERV-K loci (Type 2 proviruses), nuclear export of the unspliced HERV-K mRNA appears to be mediated by a cis-acting signal on the mRNA, the RcRE, and the protein Rec-these are analogous to the RRE-Rev system in HIV-1. Interestingly, the HIV-1 Rev protein is able to mediate the nuclear export of the HERV-K RcRE, contributing to elevated HERV-K expression in HIV-infected patients. We aimed to understand the structural basis for HIV Rev-HERV-K RcRE recognition. We examined the conformation of the RcRE RNA in solution using small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). We found that the 433-nt long RcRE can assume folded or extended conformations as observed by AFM. SAXS analysis of a truncated RcRE variant revealed an "A"-shaped topological structure similar to the one previously reported for the HIV-1 RRE. The effect of the overall topology was examined using several deletion variants. SAXS and biochemical analyses demonstrated that the "A" shape is necessary for efficient Rev-RcRE complex formation in vitro and nuclear export activity in cell culture. The findings provide insight into the mechanism of HERV-K expression and a structural explanation for HIV-1 Rev-mediated expression of HERV-K in HIV-infected patients. IMPORTANCE: Expression of the human endogenous retrovirus type K (HERV-K) has been associated with various cancers and autoimmune diseases. Nuclear export of both HIV-1 and HERV-K mRNAs is dependent on the interaction between a small viral protein (Rev in HIV-1 and Rec in HERV-K) and a region on the mRNA (RRE in HIV-1 and RcRE in HERV-K). HIV-1 Rev is able to mediate the nuclear export of RcRE-containing HERV-K mRNAs, which contributes to elevated production of HERV-K proteins in HIV-infected patients. We report the solution conformation of the RcRE RNA-the first three-dimensional topological structure for a HERV molecule-and find that the RcRE resembles the HIV-1 nuclear export signal, RRE. The finding reveals the structural basis for the increased HERV-K expression observed in HIV-infected patients. Elevated HERV expression, mediated by HIV infection or other stressors, can have various HERV-related biological consequences. The findings provide structural insight for regulation of HERV-K expression.
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Affiliation(s)
- Ina P O'Carroll
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA.
| | - Lixin Fan
- Basic Science Program, Frederick National Laboratory for Cancer Research, SAXS Core Facility of the National Cancer Institute, Frederick, MD 21702, USA
| | - Tomáš Kroupa
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Erin K McShane
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Christophe Theodore
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Elizabeth A Yates
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Benjamin Kondrup
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Jienyu Ding
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Tyler S Martin
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Alan Rein
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Yun-Xing Wang
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
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The Jembrana disease virus Rev protein: Identification of nuclear and novel lentiviral nucleolar localization and nuclear export signals. PLoS One 2019; 14:e0221505. [PMID: 31437223 PMCID: PMC6706053 DOI: 10.1371/journal.pone.0221505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/08/2019] [Indexed: 11/19/2022] Open
Abstract
The lentiviral Rev protein, which is a regulatory protein essential for virus replication, has been first studied in the human immunodeficiency virus type 1 (HIV-1). The main function of Rev is to mediate the nuclear exportation of viral RNAs. To fulfill its function, Rev shuttles between the cytoplasm and the nucleus. The Jembrana disease virus (JDV), a lentivirus, is the etiologic agent of the Jembrana disease which was first described in Bali cattle in Indonesia in 1964. Despite the high mortality rate associated with JDV, this virus remains poorly studied. Herein the subcellular distribution of JDV Rev, the nuclear and nucleolar localization signals (NLS and NoLS, respectively) and the nuclear export signal (NES) of the protein were examined. JDV Rev fused to the enhanced green fluorescent protein (EGFP) predominantly localized to the cytoplasm and nucleolus of transfected cells, as determined by fluorescence microscopy analyses. Through transfection of a series of deletion mutants of JDV Rev, it was possible to localize the NLS/NoLS region between amino acids (aa) 74 to 105. By substituting basic residues with alanine within this sequence, we demonstrated that the JDV Rev NLS encompasses aa 76 to 86, and is exclusively composed of arginine residues, whereas a bipartite NoLS was observed for the first time in any retroviral Rev/Rev-like proteins. Finally, a NES was identified downstream of the NLS/NoLS and encompasses aa 116 to 128 of the JDV Rev protein. The JDV Rev NES was found to be of the protein kinase A inhibitor (PKI) class instead of the HIV-1 Rev class. It also corresponds to the most optimal consensus sequence of PKI NES and, as such, is novel among lentiviral Rev NES.
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Schmitt K, Heyne K, Roemer K, Meese E, Mayer J. HERV-K(HML-2) rec and np9 transcripts not restricted to disease but present in many normal human tissues. Mob DNA 2015; 6:4. [PMID: 25750667 PMCID: PMC4351823 DOI: 10.1186/s13100-015-0035-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 02/12/2015] [Indexed: 01/03/2023] Open
Abstract
Background Human endogenous retroviruses of the HERV-K(HML-2) group have been associated with the development of tumor diseases. Various HERV-K(HML-2) loci encode retrovirus-like proteins, and expression of such proteins is upregulated in certain tumor types. HERV-K(HML-2)-encoded Rec and Np9 proteins interact with functionally important cellular proteins and may contribute to tumor development. Though, the biological role of HERV-K(HML-2) transcription and encoded proteins in health and disease is less understood. We therefore investigated transcription specifically of HERV-K(HML-2) rec and np9 mRNAs in a panel of normal human tissues. Results We obtained evidence for rec and np9 mRNA being present in all examined 16 normal tissue types. A total of 18 different HERV-K(HML-2) loci were identified as generating rec or np9 mRNA, among them loci not present in the human reference genome and several of the loci harboring open reading frames for Rec or Np9 proteins. Our analysis identified additional alternative splicing events of HERV-K(HML-2) transcripts, some of them encoding variant Rec/Np9 proteins. We also identified a second HERV-K(HML-2) locus formed by L1-mediated retrotransposition that is likewise transcribed in various human tissues. Conclusions HERV-K(HML-2) rec and np9 transcripts from different HERV-K(HML-2) loci appear to be present in various normal human tissues. It is conceivable that Rec and Np9 proteins and variants of those proteins are part of the proteome of normal human tissues and thus various cell types. Transcription of HERV-K(HML-2) may thus also have functional relevance in normal human cell physiology. Electronic supplementary material The online version of this article (doi:10.1186/s13100-015-0035-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katja Schmitt
- Institute of Human Genetics, Center of Human and Molecular Biology, Medical Faculty, University of Saarland, 66424 Homburg/Saar, Germany ; Sanofi-Aventis Deutschland GmbH, Industriepark Hoechst, K703, Elisabeth Kuhn Street, Frankfurt/Main, 65926 Germany
| | - Kristina Heyne
- José Carreras Research Center, Medical Faculty, University of Saarland, 66424 Homburg/Saar, Germany
| | - Klaus Roemer
- José Carreras Research Center, Medical Faculty, University of Saarland, 66424 Homburg/Saar, Germany
| | - Eckart Meese
- Institute of Human Genetics, Center of Human and Molecular Biology, Medical Faculty, University of Saarland, 66424 Homburg/Saar, Germany
| | - Jens Mayer
- Institute of Human Genetics, Center of Human and Molecular Biology, Medical Faculty, University of Saarland, 66424 Homburg/Saar, Germany ; Center of Human and Molecular Biology, University of Saarland, 66424 Homburg/Saar, Germany
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Staufen-1 interacts with the human endogenous retrovirus family HERV-K(HML-2) rec and gag proteins and increases virion production. J Virol 2013; 87:11019-30. [PMID: 23926355 DOI: 10.1128/jvi.03031-12] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The human endogenous retrovirus family HERV-K(HML-2) Rec protein is an RNA transport factor that enhances nuclear export of intron-containing retroviral transcripts. Using the yeast two-hybrid approach, we have newly identified human Staufen-1 as a Rec-interacting protein. The interaction was confirmed by coimmunoprecipitation experiments, and the relevant site in Staufen-1 has been mapped to double-stranded RNA binding domain 4 (RBD4). Staufen-1 is in several aspects functionally related to retroviral RNA transport proteins. It binds mRNAs and targets its ribonuclear cargo to polysomes for efficient translation. We observed an accumulation of Staufen-1 in the nucleus of Rec-expressing cells and colocalization in the nucleoli as well as in the cytoplasm. Overexpression of Staufen-1 resulted in a 5-fold enhancement in nuclear export and/or translation of unspliced HERV-K(HML-2) viral RNAs in the presence of Rec and its Rec-responsive element (RcRE) binding site together with a clear increase in virus production. Staufen-1 was previously shown to interact with the Gag protein of HIV-1, promoting Gag oligomerization and RNA encapsidation. We demonstrate here that Staufen-1 also binds to the Gag protein of HERV-K(HML-2). Under stress conditions, Rec colocalizes with Staufen-1 in stress granules in cells that express viral RNA but not in mRNA-decay-related processing bodies. Our results suggest a new role for Staufen-1 as a cellular Rec and HERV-K(HML-2) Gag cofactor.
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Biochemical analysis of the complex between the tetrameric export adapter protein Rec of HERV-K/HML-2 and the responsive RNA element RcRE pck30. J Virol 2012; 86:9079-87. [PMID: 22696641 DOI: 10.1128/jvi.00121-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The RNA export adaptor protein Rec, encoded for by the human endogenous retrovirus HERV-K/HML-2 elements, binds to the Rec responsive element (RcRE) located in the 3' untranslated region of HERV-K/HML-2 transcripts. Binding allows the nucleocytoplasmic export of unspliced viral RNA, thereby overcoming host restriction. Chemical probing of the secondary structure of the RcRE corroborated the theory that the RcRE forms a complex folded structure with seven stem-loop regions. Laser-induced liquid beam ion desorption mass spectrometry revealed that Rec forms stable tetramers, which are further stabilized upon RNA binding. The RNA protein complex consists of three Rec tetramers, which bind to multiple sites on the RcRE-preferentially to purine-rich motifs-which represent several low-affinity binding sites. Mutated RcREs, with one to three purine-rich motifs deleted, were still bound and exported by Rec, indicating that the complex folded structure of the RcRE is important for Rec binding. This suggests a binding model where up to three Rec tetramers bind to the complex folded structure of the RcRE and the binding seems to be tightened by recognition of the purine-rich motifs.
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Retroviral Rem protein requires processing by signal peptidase and retrotranslocation for nuclear function. Proc Natl Acad Sci U S A 2010; 107:12287-92. [PMID: 20566871 DOI: 10.1073/pnas.1004303107] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mouse mammary tumor virus (MMTV) is a complex murine retrovirus that encodes an HIV Rev-like export protein, Rem, from a doubly spliced version of envelope (Env) mRNA. Previously, the N-terminal 98-amino acid sequence of Rem, which is identical to Env signal peptide (SP), and full-length Rem were shown to be functional in a reporter assay that measures a postexport function. Here we show that MMTV-infected cells or cells transfected with rem or env cDNAs express SP, which is the active component in the reporter assay. Uncleaved Rem was partially glycosylated, but mutations in both glycosylation sites within the C terminus prevented Rem function. Mutations that reduced Rem or Env cleavage by signal peptidase greatly reduced SP levels and functional activity in the reporter assay and allowed accumulation of the uncleaved protein. Fluorescence microscopy revealed that GFP-tagged cleavage-site mutants are unstable and lack fluorescence compared with wild-type Rem, suggesting improper folding. Proteasome inhibitors allowed accumulation of uncleaved Rem relative to SP and increased reporter activity, consistent with SP retrotranslocation and proteasome escape before nuclear entry. Expression of a dominant-negative p97 ATPase did not alter levels of unprocessed Rem and SP but decreased reporter activity, suggesting p97-facilitated retrotranslocation of SP. Our results provide an example of a SP that is processed by signal peptidase and retrotranslocated to allow nuclear localization and function.
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The bovine immunodeficiency virus rev protein: identification of a novel lentiviral bipartite nuclear localization signal harboring an atypical spacer sequence. J Virol 2009; 83:12842-53. [PMID: 19828621 DOI: 10.1128/jvi.01613-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The bovine immunodeficiency virus (BIV) Rev protein (186 amino acids [aa] in length) is involved in the nuclear exportation of partially spliced and unspliced viral RNAs. Previous studies have shown that BIV Rev localizes in the nucleus and nucleolus of infected cells. Here we report the characterization of the nuclear/nucleolar localization signals (NLS/NoLS) of this protein. Through transfection of a series of deletion mutants of BIV Rev fused to enhanced green fluorescent protein and fluorescence microscopy analyses, we were able to map the NLS region between aa 71 and 110 of the protein. Remarkably, by conducting alanine substitution of basic residues within the aa 71 to 110 sequence, we demonstrated that the BIV Rev NLS is bipartite, maps to aa 71 to 74 and 95 to 101, and is predominantly composed of arginine residues. This is the first report of a bipartite Rev (or Rev-like) NLS in a lentivirus/retrovirus. Moreover, this NLS is atypical, as the length of the sequence between the motifs composing the bipartite NLS, e.g., the spacer sequence, is 20 aa. Further mutagenesis experiments also identified the NoLS region of BIV Rev. It localizes mainly within the NLS spacer sequence. In addition, the BIV Rev NoLS sequence differs from the consensus sequence reported for other viral and cellular nucleolar proteins. In summary, we conclude that the nucleolar and nuclear localizations of BIV Rev are mediated via novel NLS and NoLS motifs.
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Mertz JA, Chadee AB, Byun H, Russell R, Dudley JP. Mapping of the functional boundaries and secondary structure of the mouse mammary tumor virus Rem-responsive element. J Biol Chem 2009; 284:25642-52. [PMID: 19632991 DOI: 10.1074/jbc.m109.012476] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mouse mammary tumor virus (MMTV) is a complex retrovirus that encodes at least three regulatory and accessory proteins, including Rem. Rem is required for nuclear export of unspliced viral RNA and efficient expression of viral proteins. Our previous data indicated that sequences at the envelope-3' long terminal repeat junction are required for proper export of viral RNA. To further map the Rem-responsive element (RmRE), reporter vectors containing various portions of the viral envelope gene and the 3' long terminal repeat were tested in the presence and absence of Rem in transient transfection assays. A 476-bp fragment that spans the envelope-long terminal repeat junction had activity equivalent to the entire 3'-end of the mouse mammary tumor virus genome, but further deletions at the 5'- or 3'-ends reduced Rem responsiveness. RNase structure mapping of the full-length RmRE and a 3'-truncation suggested multiple domains with local base pairing and intervening single-stranded segments. A secondary structure model constrained by these data is reminiscent of the RNA response elements of other complex retroviruses, with numerous local stem-loops and long-range base pairs near the 5'- and 3'-boundaries, and differs substantially from an earlier model generated without experimental constraints. Covariation analysis provides limited support for basic features of our model. Reporter assays in human and mouse cell lines revealed similar boundaries, suggesting that the RmRE does not require cell type-specific proteins to form a functional structure.
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Affiliation(s)
- Jennifer A Mertz
- Section of Molecular Genetics and Microbiology, The University of Texas, Austin, Texas 78712-0162, USA
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The RNA transport element RTE is essential for IAP LTR-retrotransposon mobility. Virology 2008; 377:88-99. [PMID: 18485438 DOI: 10.1016/j.virol.2008.04.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 03/17/2008] [Accepted: 04/03/2008] [Indexed: 11/21/2022]
Abstract
We previously identified an RNA transport element (RTE) present at a high copy number in the mouse genome. Here, we show that a related element, RTE-D, is part of a mobile LTR-retrotransposon, which belongs to a family of intracisternal A-particle related elements (IAP). We demonstrate that RTE-D is essential for the mobility of the retrotransposon and it can be substituted by other known RNA export signals. RTE-deficient IAP transcripts are retained in the nucleus, while the RTE-containing transcripts accumulate in the cytoplasm allowing Gag protein expression. RTE-D acts as a posttranscriptional control element in a heterologous reporter mRNA and is activated by the cellular RNA binding protein 15 (RBM15), as reported for the previously described RTE. We identified a complex family of RTE-containing IAPs in mouse and mapped the active RTE-D-containing IAPs to the Mmr10 group of LTR-retrotransposons. These data reveal that, despite a complex evolutionary history, retroelements and retroviruses share the dependency on posttranscriptional regulation.
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Lee YN, Bieniasz PD. Reconstitution of an infectious human endogenous retrovirus. PLoS Pathog 2007; 3:e10. [PMID: 17257061 PMCID: PMC1781480 DOI: 10.1371/journal.ppat.0030010] [Citation(s) in RCA: 220] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Accepted: 12/13/2006] [Indexed: 12/29/2022] Open
Abstract
The human genome represents a fossil record of ancient retroviruses that once replicated in the ancestors of contemporary humans. Indeed, approximately 8% of human DNA is composed of sequences that are recognizably retroviral. Despite occasional reports associating human endogenous retrovirus (HERV) expression with human disease, almost all HERV genomes contain obviously inactivating mutations, and none are thought to be capable of replication. Nonetheless, one family of HERVs, namely HERV-K(HML-2), may have replicated in human ancestors less than 1 million years ago. By deriving a consensus sequence, we reconstructed a proviral clone (HERV-KCON) that likely resembles the progenitor of HERV-K(HML-2) variants that entered the human genome within the last few million years. We show that HERV-KCON Gag and protease proteins mediate efficient assembly and processing into retrovirus-like particles. Moreover, reporter genes inserted into the HERV-KCON genome and packaged into HERV-K particles are capable of infectious transfer and stable integration in a manner that requires reverse transcription. Additionally, we show that HERV-KCON Env is capable of pseudotyping HIV-1 particles and mediating entry into human and nonhuman cell lines. Furthermore, we show that HERV-KCON is resistant to inhibition by the human retrovirus restriction factors tripartite motif 5α and apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) 3G but is inhibited by APOBEC 3F. Overall, the resurrection of this extinct infectious agent in a functional form from molecular fossils should enable studies of the molecular virology and pathogenic potential of this ancient human retrovirus. Retrovirus genomes integrate into the genomes of host cells. If the target cells of a particular retrovirus include germ-line cells, e.g., sperm or egg cells, then retroviral genomes can be inherited like cellular genes. So-called “endogenous” retroviruses have accumulated throughout evolution in the genomes of many organisms, including humans. While all known endogenous retroviruses of modern humans are unable to replicate as retroviruses, the human genome represents a fossil record of ancient retroviruses that once infected our ancestors. In this study, a collection of “dead” endogenous retroviral genomes in modern human DNA was used to deduce the approximate sequence of an ancestral retrovirus, human endogenous retrovirus (HERV)-K, that is now thought to be extinct. A pseudo-ancestral HERV-K DNA sequence was synthesized and used to produce viral proteins and RNA that could reconstitute the HERV-K replication cycle. Thus, the replication and biology of a once-extinct retrovirus can now be studied in the laboratory. Interestingly, reconstituted HERV-K replication experiments, and comparison of the reconstituted HERV-K DNA sequence with the dead HERV-Ks in modern human DNA, suggests that HERV-K may have been extinguished in humans in part by host defenses that induce mutation of retroviral DNA and that the reconstitution of the pseudo-ancestral HERV-K reversed these changes.
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Affiliation(s)
- Young Nam Lee
- Aaron Diamond AIDS Research Center, The Rockefeller University, New York, New York, United States of America
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Paul D Bieniasz
- Aaron Diamond AIDS Research Center, The Rockefeller University, New York, New York, United States of America
- Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
- * To whom correspondence should be addressed. E-mail:
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Wang-Johanning F, Liu J, Rycaj K, Huang M, Tsai K, Rosen DG, Chen DT, Lu DW, Barnhart KF, Johanning GL. Expression of multiple human endogenous retrovirus surface envelope proteins in ovarian cancer. Int J Cancer 2007; 120:81-90. [PMID: 17013901 DOI: 10.1002/ijc.22256] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Individual classes of human endogenous retrovirus (HERV) genes and proteins are expressed in cancer, but expression of more than one type of HERV is rare. We report here the expression of multiple HERV genes and proteins in ovarian cell lines and tissues. Expression of HERV-K env mRNA was greater in ovarian epithelial tumors than in normal ovarian tissues (N = 254). The expression of this protein on the surface and in the cytoplasm of ovarian cancer cells was confirmed using anti-HERV-K specific antibody by flow cytometric analysis. The frequency of expression of HERV-K env protein in multitissue microarrays (N = 641) was determined by immunohistochemistry and a significant correlation with tumor histotype was found. A significantly increased expression of HERV-K was observed in tumors with low malignant potential and low grade, relative to expression in normal ovarian tissues. The increase in expression of HERV-K env protein took place in a stepwise fashion in serous papillary adenocarcinoma. Interestingly, we found that other classes of HERV env mRNAs, including ERV3 and HERV-E, are expressed in the same ovarian cancer tissues that expressed HERV-K. Furthermore, anti-HERV antibodies including anti-ERV3 (30%), anti-HERV-E (40%) and anti-HERV-K (55%) were detected in patients with ovarian cancer, but not in normal female controls. HERV env proteins are frequently transcribed and translated in ovarian epithelial tumors, and multiple HERV families are detectable in ovarian cancer. HERV env proteins, and especially those expressed on the cell surface, may serve as novel tumor targets for detection, diagnosis and immunotherapy of ovarian cancer.
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MESH Headings
- Adenocarcinoma, Clear Cell/metabolism
- Adenocarcinoma, Clear Cell/virology
- Adenocarcinoma, Mucinous/metabolism
- Adenocarcinoma, Mucinous/virology
- Adult
- Aged
- Aged, 80 and over
- Amino Acid Sequence
- Base Sequence
- Carcinoma, Endometrioid/metabolism
- Carcinoma, Endometrioid/virology
- Case-Control Studies
- Cystadenocarcinoma, Serous/metabolism
- Cystadenocarcinoma, Serous/virology
- Endogenous Retroviruses/genetics
- Endogenous Retroviruses/immunology
- Endogenous Retroviruses/metabolism
- Enzyme-Linked Immunosorbent Assay
- Female
- Flow Cytometry
- Fluorescent Antibody Technique
- Gene Products, env/genetics
- Gene Products, env/metabolism
- Gene Products, env/physiology
- Humans
- Immunoenzyme Techniques
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Middle Aged
- Molecular Sequence Data
- Ovarian Neoplasms/metabolism
- Ovarian Neoplasms/virology
- Ovary/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Tissue Array Analysis
- Tumor Cells, Cultured
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Affiliation(s)
- Feng Wang-Johanning
- Department of Veterinary Sciences and Michale E. Keeling Center for Comparative Medicine and Research, University of Texas MD Anderson Cancer Center, Houston, TX 78602, USA.
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14
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Felber BK, Zolotukhin AS, Pavlakis GN. Posttranscriptional Control of HIV‐1 and Other Retroviruses and Its Practical Applications. ADVANCES IN PHARMACOLOGY 2007; 55:161-97. [PMID: 17586315 DOI: 10.1016/s1054-3589(07)55005-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Barbara K Felber
- Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, USA
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15
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Büscher K, Hahn S, Hofmann M, Trefzer U, Ozel M, Sterry W, Löwer J, Löwer R, Kurth R, Denner J. Expression of the human endogenous retrovirus-K transmembrane envelope, Rec and Np9 proteins in melanomas and melanoma cell lines. Melanoma Res 2006; 16:223-34. [PMID: 16718269 DOI: 10.1097/01.cmr.0000215031.07941.ca] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The human endogenous retrovirus-K encodes two potential tumor proteins, Rec and Np9. Rec is related to the Rev protein of HIV-1 and has been shown to be associated with tumor development in nude mice. Having shown the expression of human endogenous retrovirus-K in human melanomas and melanoma cell lines, tools were developed to allow the expression of the transmembrane envelope, Rec and Np9 mRNA and proteins to be studied in more detail. The expression of spliced env, rec and np9 was investigated by reverse transcriptase-polymerase chain reaction using a set of primers developed to discriminate between full-length and spliced mRNA. Env-specific, Rec-specific and Np9-specific antisera were produced, characterized and used to study protein expression in melanomas and melanoma cell lines by immunohistochemistry, immunofluorescence and Western blot analyses. Existence of human endogenous retrovirus-K Rec and Np9-specific antibodies in the sera of melanoma patients were analyzed by Western blot of immunofluorescence studies. The expression of both spliced env and rec mRNA was detected in 39% of the melanomas and in 40% of the melanoma cell lines and np9 mRNA was detected in 29 and 21%, respectively. In normal neonatal melanocytes, spliced rec mRNA was detected in the absence of spliced env mRNA. Using antisera specific for Rec and Np9, Rec protein was found in 14% of the melanomas but Np9 in none. In addition, cell surface expression of the putatively immunosuppressive transmembrane envelope protein and release of virus particles were shown. Antibodies specific for neither Rec nor Np9 were detected. The transmembrane envelope protein, Rec and Np9 proteins are expressed in melanoma cells with a pattern similar to that seen in teratocarcinoma cell lines. Additional experiments are needed to determine their involvement, if any, in cell proliferation and tumor progression.
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16
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Mertz JA, Simper MS, Lozano MM, Payne SM, Dudley JP. Mouse mammary tumor virus encodes a self-regulatory RNA export protein and is a complex retrovirus. J Virol 2006; 79:14737-47. [PMID: 16282474 PMCID: PMC1287593 DOI: 10.1128/jvi.79.23.14737-14747.2005] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Mouse mammary tumor virus (MMTV) has been classified as a simple retrovirus with two accessory genes, dut and sag. Cloned MMTV proviruses carrying a trimethoprim (trim) cassette in the envelope gene were defective for Gag protein production and the nuclear export of unspliced gag-pol RNA. Complementation experiments indicated that a trans-acting product was responsible for the Gag defect of such mutants. Analysis of MMTV-infected cells revealed the presence of a novel, doubly spliced RNA that encodes a putative product of 301 amino acids. Overexpression of cDNA from this RNA increased Gag levels from env mutant proviruses or reporter gene expression from unspliced mRNAs and allowed detection of a 33-kDa protein product, which has been named regulator of export of MMTV mRNA, or Rem. The Rem N terminus has motifs similar to the Rev-like export proteins of complex retroviruses, and mutation of the nuclear localization signal (NLS) abolished RNA export and detection within the nucleus. The Rem C terminus has few identifiable features, but removal of this domain increased Rem-mediated export, suggesting an autoregulatory function. A reporter vector developed from the 3' end of the MMTV provirus was Rem responsive and required both the presence of the MMTV env-U3 junction and a functional Crm1 pathway. The identification of a third accessory protein from a doubly spliced transcript suggests that MMTV is the first murine complex retrovirus to be documented. Manipulation of the MMTV genome may provide mouse models for human retroviral diseases, such as AIDS.
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Affiliation(s)
- Jennifer A Mertz
- The University of Texas at Austin, Section of Molecular Genetics and Microbiology, One University Station, A5000, Austin, TX 78712, USA
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17
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Seifarth W, Frank O, Zeilfelder U, Spiess B, Greenwood AD, Hehlmann R, Leib-Mösch C. Comprehensive analysis of human endogenous retrovirus transcriptional activity in human tissues with a retrovirus-specific microarray. J Virol 2005; 79:341-52. [PMID: 15596828 PMCID: PMC538696 DOI: 10.1128/jvi.79.1.341-352.2005] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Retrovirus-like sequences account for 8 to 9% of the human genome. Among these sequences, about 8,000 pol-containing proviral elements have been identified to date. As part of our ongoing search for active and possibly disease-relevant human endogenous retroviruses (HERVs), we have recently developed an oligonucleotide-based microarray. The assay allows for both the detection and the identification of most known retroviral reverse transcriptase (RT)-related nucleic acids in biological samples. In the present study, we have investigated the transcriptional activity of representative members of 20 HERV families in 19 different normal human tissues. Qualitative evaluation of chip hybridization signals and quantitative analysis by real-time RT-PCR revealed distinct HERV activity in the human tissues under investigation, suggesting that HERV elements are active in human cells in a tissue-specific manner. Most active members of HERV families were found in mRNA prepared from skin, thyroid gland, placenta, and tissues of reproductive organs. In contrast, only few active HERVs were detectable in muscle cells. Human tissues that lack HERV transcription could not be found, confirming that human endogenous retroviruses are permanent components of the human transcriptome. Distinct activity patterns may reflect the characteristics of the regulatory machinery in these cells, e.g., cell type-dependent occurrence of transcriptional regulatory factors.
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Affiliation(s)
- Wolfgang Seifarth
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany.
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18
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Freed EO, Ross SR. Retroviruses 2004: review of the 2004 Cold Spring Harbor Retroviruses Conference. Retrovirology 2004; 1:25. [PMID: 15357866 PMCID: PMC519032 DOI: 10.1186/1742-4690-1-25] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Accepted: 09/09/2004] [Indexed: 12/14/2022] Open
Abstract
For the past several decades, retrovirologists from around the world have gathered in late May at the Cold Spring Harbor Laboratories in New York to present their studies in formal talks and posters, and to discuss their ongoing research informally at the bar or on the beach. As organizers of the 2004 Cold Spring Harbor Retroviruses Conference, we have been asked by the editors of Retrovirology to prepare a review of the meeting for publication on-line. Our goal in this review is not to provide a detailed description of data presented at the meeting but rather to highlight some of the significant developments reported this year. The review is structured in a manner that parallels the organization of the meeting; beginning with the entry phase of the replication cycle, proceeding with post-entry events, assembly and release, integration, reverse transcription, pathogenesis/host factors, RNA-related events (transcription, processing, export, and packaging) and finishing with antivirals. While the most striking developments this year involved post-entry events and assembly/release, significant progress was made towards elucidating a number of aspects of the retroviral replication cycle.
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Affiliation(s)
- Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute at Frederick, National Institutes of Health, Bg. 535/Rm. 108, Frederick, MD 21702-1201, USA
| | - Susan R Ross
- University of Pennsylvania School of Medicine, Room 313 BRBII/III, 421 Curie Blvd., Philadelphia, PA 19104-6142, USA
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19
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Mayer J, Ehlhardt S, Seifert M, Sauter M, Müller-Lantzsch N, Mehraein Y, Zang KD, Meese E. Human endogenous retrovirus HERV-K(HML-2) proviruses with Rec protein coding capacity and transcriptional activity. Virology 2004; 322:190-8. [PMID: 15063128 DOI: 10.1016/j.virol.2004.01.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Revised: 01/09/2004] [Accepted: 01/26/2004] [Indexed: 11/17/2022]
Abstract
The human endogenous retrovirus family HERV-K(HML-2) encodes the so-called Rec protein that displays functional similarities to the HIV(REV) protein. The number of proviruses producing Rec protein was hitherto unknown. We therefore analyzed the human genome sequence data and determined seven HERV-K(HML-2) proviruses potentially capable of producing Rec both on the mRNA and the protein level. We analyzed Rec mRNA expression in the Tera-1 cell line and in synovial tissue, and in the expressed sequence tag (EST) database. Diagnostic nucleotides assigned transcriptionally active and Rec-encoding proviruses to human chromosomes 6, 7, 11, and 12. Differently spliced mRNAs were also identified. The various active proviruses encode almost identical Rec proteins. Our study contributes to the understanding of the biology of HERV-K(HML-2) Rec protein. Our study further demonstrates that minor sequence differences among proviruses allow assigning HERV transcripts to particular proviral loci. Extended studies will eventually yield a more complete image of HERV transcription, regulation, and biological significance in diverse human tissues.
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Affiliation(s)
- Jens Mayer
- Department of Human Genetics, Medical Faculty, University of Saarland, 66421 Homburg/Saar, Germany.
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20
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Seifarth W, Spiess B, Zeilfelder U, Speth C, Hehlmann R, Leib-Mösch C. Assessment of retroviral activity using a universal retrovirus chip. J Virol Methods 2003; 112:79-91. [PMID: 12951215 DOI: 10.1016/s0166-0934(03)00194-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A DNA chip-based assay is described for parallel detection and identification of a wide variety of human and mammalian exogenous and endogenous retroviruses. The assay combines multiplex polymerase chain reaction (PCR) using fluorochrome-modified primer mixtures and chip hybridization. The microarray is composed of retrovirus-specific synthetic oligonucleotides as capture probes deposited on glass slides. The retrovirus chip can be used to assess the occurrence of reverse transcriptase (RT)-related transcripts in biological samples of human and mammalian origin. For example, distinct expression profiles of human endogenous retroviruses (HERV) were established reproducibly in human white blood cells, mammary gland and other human tissues. In particles released by human cells, packaging of specific HERV transcripts could be observed. Monitoring of human exogenous retroviruses (HIV, HTLV) and detection of putative cross-species transmissions (MLV, PERV) in human samples was efficient and reliable. The DNA chip should be an excellent tool for the detection of most relevant retroviruses and offers insights into differential retroviral activities and replication strategies. Furthermore, it could improve significantly the safety of gene therapy, tissue engineering, xenotransplantation and production of therapeutic polypeptides in cell culture.
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Affiliation(s)
- Wolfgang Seifarth
- Medical Clinic III, Faculty of Clinical Medicine Mannheim, University of Heidelberg, D-68305, Mannheim, Germany.
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21
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Wang-Johanning F, Frost AR, Jian B, Epp L, Lu DW, Johanning GL. Quantitation of HERV-K env gene expression and splicing in human breast cancer. Oncogene 2003; 22:1528-35. [PMID: 12629516 DOI: 10.1038/sj.onc.1206241] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Human endogenous retroviruses (HERVs) comprise up to 8% of the human genome. In previous studies, we demonstrated that type 1 HERV-K envelope (env) transcripts are expressed in most human breast cancers, but not in normal breast tissues. In the current study, we report that type 2 HERV-K env transcripts are also present in human breast cancers. By real-time RT-PCR, the expression of HERV-K env transcripts was 5-10-fold higher in breast cancer cell lines treated with estradiol and progesterone than in cells without treatment, and expression was significantly higher in most breast cancer tissues than in normal breast tissues. Furthermore, both types of HERV-K env transcripts were capable of being spliced into subgenomic env transcripts and various splice donor and acceptor sites were detected in breast cancers. The selective expression and distribution of multiple HERV-K endogenous retroviral element splice variants in breast cancer, but not in normal controls, suggests that they are novel breast tumor markers.
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MESH Headings
- Breast Neoplasms/drug therapy
- Breast Neoplasms/genetics
- Breast Neoplasms/pathology
- Carcinoma, Intraductal, Noninfiltrating/drug therapy
- Carcinoma, Intraductal, Noninfiltrating/genetics
- Carcinoma, Intraductal, Noninfiltrating/pathology
- Codon, Terminator
- Endogenous Retroviruses/genetics
- Epithelial Cells/physiology
- Estradiol/pharmacology
- Female
- Gene Expression Regulation, Neoplastic/drug effects
- Gene Products, env/analysis
- Gene Products, env/genetics
- Humans
- Progesterone/pharmacology
- RNA Splicing
- Reference Values
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Tumor Cells, Cultured
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Affiliation(s)
- Feng Wang-Johanning
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA.
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22
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Magin-Lachmann C, Hahn S, Strobel H, Held U, Löwer J, Löwer R. Rec (formerly Corf) function requires interaction with a complex, folded RNA structure within its responsive element rather than binding to a discrete specific binding site. J Virol 2001; 75:10359-71. [PMID: 11581404 PMCID: PMC114610 DOI: 10.1128/jvi.75.21.10359-10371.2001] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It was recently reported that the human endogenous retrovirus HTDV/HERV-K encodes the regulatory protein Rec (formerly designated Corf), which is functionally equivalent to the nuclear export adapter proteins Rev of human immunodeficiency virus and Rex of human T-cell leukemia virus. We have demonstrated that the Rec protein interacts with a characteristic 429-nucleotide RNA element, the Rec-responsive element (RcRE), present in the 3' long terminal repeat of HTDV/HERV-K transcripts. In analogy to the Rev and Rex proteins, which have distinct RNA binding sites in their responsive elements, we have proposed that Rec may also have a defined binding site in the RcRE. In this report, we demonstrate that not every HTDV/HERV-K copy present in the human genome contains an active RcRE, and we characterize mutations that abrogate Rec function. In addition, we demonstrate that Rec function requires binding to a complex, folded RNA structure rather than binding to a discrete specific binding site, in contrast to Rev and Rex and their homologous responsive elements. We define four stem-loop structures in the RcRE that are essential for Rec function. Finally, we demonstrate that both Rev and Rex can mediate nuclear export through the RcRE but that their binding sites are different from each other and from that of Rec.
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23
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Boese A, Galli U, Geyer M, Sauter M, Mueller-Lantzsch N. The Rev/Rex homolog HERV-K cORF multimerizes via a C-terminal domain. FEBS Lett 2001; 493:117-21. [PMID: 11287007 DOI: 10.1016/s0014-5793(01)02280-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Expression of human endogenous retrovirus K (HERV-K) is associated with germ-cell neoplasia. HERV-K encodes a protein of the Rev/Rex family, cORF, that supports cellular transformation and binds the promyelocytic leukemia zinc finger (PLZF) protein implicated in spermatogenesis. Rev/Rex function invariably depends on multimerization. Here we show that cORF likewise self-associates to form higher-order oligomers. Amino acids (aa) 47-87 in cORF are sufficient, aa 75-87 essential for self-association. Consistently, this domain is predicted to form a hydrophobic alpha-helix that may represent an oligomerization interface. The existence of a dimerization-competent cORF mutant lacking PLZF-binding activity (cORF47-87) suggests a way of dominant negative inhibition of the proposed tumor susceptibility factor cORF.
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Affiliation(s)
- A Boese
- Institut für Medizinische Mikrobiologie und Hygiene, Abteilung, Virologie, Haus 47, 66421 Hamburg, Germany
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