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Journal of Virology Sep 2020Retroviral envelope glycoprotein (Env) is essential for the specific recognition of the host cell and the initial phase of infection. As reported for human...
Retroviral envelope glycoprotein (Env) is essential for the specific recognition of the host cell and the initial phase of infection. As reported for human immunodeficiency virus (HIV), the recruitment of Env into a retroviral membrane envelope is mediated through its interaction with a Gag polyprotein precursor of structural proteins. This interaction, occurring between the matrix domain (MA) of Gag and the cytoplasmic tail (CT) of the transmembrane domain of Env, takes place at the host cell plasma membrane. To determine whether the MA of Mason-Pfizer monkey virus (M-PMV) also interacts directly with the CT of Env, we mimicked the conditions in an experiment by using a CT in its physiological trimeric conformation mediated by the trimerization motif of the GCN4 yeast transcription factor. The MA protein was used at the concentration shifting the equilibrium to its trimeric form. The direct interaction between MA and CT was confirmed by a pulldown assay. Through the combination of nuclear magnetic resonance (NMR) spectroscopy and protein cross-linking followed by mass spectrometry analysis, the residues involved in mutual interactions were determined. NMR has shown that the C terminus of the CT is bound to the C-terminal part of MA. In addition, protein cross-linking confirmed the close proximity of the N-terminal part of CT and the N terminus of MA, which is enabled by their location at the membrane. These results are in agreement with the previously determined orientation of MA on the membrane and support the already observed mechanisms of M-PMV virus-like particle transport and budding. By a combination of nuclear magnetic resonance (NMR) and mass spectroscopy of cross-linked peptides, we show that in contrast to human immunodeficiency virus type 1 (HIV-1), the C-terminal residues of the unstructured cytoplasmic tail of Mason-Pfizer monkey virus (M-PMV) Env interact with the matrix domain (MA). Based on biochemical data and molecular modeling, we propose that individual cytoplasmic tail (CT) monomers of a trimeric complex bind MA molecules belonging to different neighboring trimers, which may stabilize the MA orientation at the membrane by the formation of a membrane-bound net of interlinked Gag and CT trimers. This also corresponds with the concept that the membrane-bound MA of Gag recruits Env through interaction with the full-length CT, while CT truncation during maturation attenuates the interaction to facilitate uncoating. We propose a model suggesting different arrangements of MA-CT complexes between a D-type and C-type retroviruses with short and long CTs, respectively.
Topics: Gene Products, env; Gene Products, gag; Mason-Pfizer monkey virus; Protein Domains
PubMed: 32796061
DOI: 10.1128/JVI.01146-20 -
Virology Aug 2013Transcriptome analysis of polar bears (Ursus maritimus) yielded sequences with highest similarity to the human endogenous retrovirus group HERV-K(HML-2). Further...
Transcriptome analysis of polar bears (Ursus maritimus) yielded sequences with highest similarity to the human endogenous retrovirus group HERV-K(HML-2). Further analysis of the polar bear draft genome identified an endogenous betaretrovirus group comprising 26 proviral copies and 231 solo LTRs. Molecular dating indicates the group originated before the divergence of bears from a common ancestor but is not present in all carnivores. Closely related sequences were identified in the giant panda (Ailuropoda melanoleuca) and characterized from its genome. We have designated the polar bear and giant panda sequences U. maritimus endogenous retrovirus (UmaERV) and A. melanoleuca endogenous retrovirus (AmeERV), respectively. Phylogenetic analysis demonstrated that the bear virus group is nested within the HERV-K supergroup among bovine and bat endogenous retroviruses suggesting a complex evolutionary history within the HERV-K group. All individual remnants of proviral sequences contain numerous frameshifts and stop codons and thus, the virus is likely non-infectious.
Topics: Amino Acid Sequence; Animals; Base Sequence; Betaretrovirus; Cluster Analysis; Evolution, Molecular; Molecular Sequence Data; Phylogeny; Proviruses; Terminal Repeat Sequences; Ursidae
PubMed: 23725819
DOI: 10.1016/j.virol.2013.05.008 -
Scientific Reports Aug 2018MPMV precursor polypeptide Pr78 orchestrates assembly and packaging of genomic RNA (gRNA) into virus particles. Therefore, we have expressed recombinant full-length Pr78...
MPMV precursor polypeptide Pr78 orchestrates assembly and packaging of genomic RNA (gRNA) into virus particles. Therefore, we have expressed recombinant full-length Pr78 either with or without His-tag in bacterial as well as eukaryotic cultures and purified the recombinant protein from soluble fractions of the bacterial cultures. The recombinant Pr78 protein has the intrinsic ability to assemble in vitro to form virus like particles (VLPs). Consistent with this observation, the recombinant protein could form VLPs in both prokaryotes and eukaryotes. VLPs formed in eukaryotic cells by recombinant Pr78 with or without His-tag can encapsidate MPMV transfer vector RNA, suggesting that the inclusion of the His-tag to the full-length Pr78 did not interfere with its expression or biological function. This study demonstrates the expression and purification of a biologically active, recombinant Pr78, which should pave the way to study RNA-protein interactions involved in the MPMV gRNA packaging process.
Topics: Gene Expression; Gene Products, gag; HEK293 Cells; Humans; Mason-Pfizer monkey virus; Recombinant Proteins
PubMed: 30087395
DOI: 10.1038/s41598-018-30142-0 -
Aging Jul 2020The betaretrovirus Mouse Mammary Tumor Virus (MMTV) is the well characterized etiological agent of mammary tumors in mice. In contrast, the etiology of sporadic human...
The betaretrovirus Mouse Mammary Tumor Virus (MMTV) is the well characterized etiological agent of mammary tumors in mice. In contrast, the etiology of sporadic human breast cancer (BC) is unknown, but accumulating data indicate a possible viral origin also for these malignancies. The presence of MMTV-like sequences (MMTVels) in the human salivary glands and saliva supports the latter as possible route of inter-human dissemination. In the absence of the demonstration of a mouse-man transmission of MMTV, we considered the possibility that a cross-species transmission could have occurred in ancient times. Therefore, we investigated MMTVels in the ancient dental calculus, which originates from saliva and is an excellent material for paleovirology. The calculus was collected from 36 ancient human skulls, excluding any possible mouse contamination. MMTV-like sequences were identified in the calculus of 6 individuals dated from the Copper Age to the 17 century. The MMTV-like sequences were compared with known human endogenous betaretroviruses and with animal exogenous betaretroviruses, confirming their exogenous origin and relation to MMTV. These data reveal that a human exogenous betaretrovirus similar to MMTV has existed at least since 4,500 years ago and indirectly support the hypothesis that it could play a role in human breast cancer.
Topics: Adolescent; Adult; Animals; Betaretrovirus; Breast Neoplasms; Breast Neoplasms, Male; Cell Transformation, Viral; DNA, Viral; Female; History, 15th Century; History, 16th Century; History, 17th Century; History, Ancient; History, Medieval; Humans; Male; Mammary Tumor Virus, Mouse; Middle Aged; Phylogeny; Retroviridae Infections; Tumor Virus Infections; Viral Zoonoses; Young Adult
PubMed: 32735554
DOI: 10.18632/aging.103780 -
Veterinary Research 2007Jaagsiekte Sheep Retrovirus (JSRV) is a betaretrovirus infecting sheep. This virus is responsible for a pulmonary adenocarcinoma, by transformation of epithelial cells... (Review)
Review
Jaagsiekte Sheep Retrovirus (JSRV) is a betaretrovirus infecting sheep. This virus is responsible for a pulmonary adenocarcinoma, by transformation of epithelial cells from the bronchioli and alveoli. This animal cancer is similar to human bronchioloalveolar cancer (BAC), a specific form of human lung cancer for which a viral aetiology has not yet been identified. JSRV interacts with target cells through the membrane receptor Hyal2. The JSRV genome is simple and contains no recognised oncogene. It is now well established that the viral envelope protein is oncogenic by itself, via the cytoplasmic domain of the transmembrane glycoprotein and some domains of the surface glycoprotein. Activation of the PI3K/Akt and MAPK pathways participates in the envelope-induced transformation. Tumour development is associated with telomerase activation. This review will focus on the induction of cancer by JSRV.
Topics: Animals; Jaagsiekte sheep retrovirus; Lung Neoplasms; Pulmonary Adenomatosis, Ovine; Sheep
PubMed: 17257570
DOI: 10.1051/vetres:2006060 -
Retrovirology Mar 2013Betaretroviruses infect a wide range of species including primates, rodents, ruminants, and marsupials. They exist in both endogenous and exogenous forms and are...
BACKGROUND
Betaretroviruses infect a wide range of species including primates, rodents, ruminants, and marsupials. They exist in both endogenous and exogenous forms and are implicated in animal diseases such as lung cancer in sheep, and in human disease, with members of the human endogenous retrovirus-K (HERV-K) group of endogenous betaretroviruses (βERVs) associated with human cancers and autoimmune diseases. To improve our understanding of betaretroviruses in an evolutionarily distinct host species, we characterized βERVs present in the genomes and transcriptomes of mega- and microbats, which are an important reservoir of emerging viruses.
RESULTS
A diverse range of full-length βERVs were discovered in mega- and microbat genomes and transcriptomes including the first identified intact endogenous retrovirus in a bat. Our analysis revealed that the genus Betaretrovirus can be divided into eight distinct sub-groups with evidence of cross-species transmission. Betaretroviruses are revealed to be a complex retrovirus group, within which one sub-group has evolved from complex to simple genomic organization through the acquisition of an env gene from the genus Gammaretrovirus. Molecular dating suggests that bats have contended with betaretroviral infections for over 30 million years.
CONCLUSIONS
Our study reveals that a diverse range of betaretroviruses have circulated in bats for most of their evolutionary history, and cluster with extant betaretroviruses of divergent mammalian lineages suggesting that their distribution may be largely unrestricted by host species barriers. The presence of βERVs with the ability to transcribe active viral elements in a major animal reservoir for viral pathogens has potential implications for public health.
Topics: Animals; Betaretrovirus; Chiroptera; Cluster Analysis; DNA, Viral; Endogenous Retroviruses; Evolution, Molecular; Phylogeny; Sequence Analysis, DNA
PubMed: 23537098
DOI: 10.1186/1742-4690-10-35 -
Journal of Virology Feb 2011Sequences of retroviral origin occupy approximately 10% of mammalian genomes. Various infectious endogenous retroviruses (ERVs) and functional retroviral elements have...
Sequences of retroviral origin occupy approximately 10% of mammalian genomes. Various infectious endogenous retroviruses (ERVs) and functional retroviral elements have been reported for several mammals but not cattle. Here, we identified two proviruses, designated bovine endogenous retrovirus K1 (BERV-K1) and BERV-K2, containing full-length envelope (env) genes in the bovine genome. Phylogenetic analysis revealed that they belong to the genus Betaretrovirus. By reverse transcription (RT)-PCR, both BERV-K1 and -K2 env mRNAs were detected in the placenta and cultured bovine trophoblast cells. Real-time RT-PCR analysis using RNAs isolated from various bovine tissues revealed that BERV-K1 env mRNA was preferentially expressed in the placenta. Moreover, we also found the expression of doubly spliced transcripts, named the REBK1 and REBK2 genes. Both the REBK1 and REBK2 proteins have motifs for a putative nuclear localization signal and a nuclear export signal. REBK1 and REBK2 fused with green fluorescent proteins were localized mainly in the nuclei when they were expressed in bovine and porcine cells. In the env and 3' long terminal repeats of BERV-K1 and -K2, we found regulatory elements responsible for the splicing and transport of viral RNAs and/or translation of the env genes. Although we have not identified the expressed Env proteins in bovine tissues, these data suggest that both BERV-K1 and BERV-K2 express Env proteins and that these proteins may have physiological functions in vivo.
Topics: Animals; Betaretrovirus; Carrier State; Cattle; Cells, Cultured; Cluster Analysis; DNA, Viral; Endogenous Retroviruses; Female; Molecular Sequence Data; Phylogeny; Placenta; Pregnancy; RNA, Viral; Retroviridae Infections; Reverse Transcriptase Polymerase Chain Reaction; Sequence Analysis, DNA; Sequence Homology; Transcription, Genetic; Trophoblasts
PubMed: 21084469
DOI: 10.1128/JVI.01234-10 -
Journal of Medical Primatology Aug 2017To better understand Simian betaretrovirus (SRV) seropositivity in virus-negative macaques, we transfused blood from SRV-infected or suspect donors into immunosuppressed...
To better understand Simian betaretrovirus (SRV) seropositivity in virus-negative macaques, we transfused blood from SRV-infected or suspect donors into immunosuppressed naive recipients. Our results do not support typical SRV1-5 infection as the cause, but provide evidence for several possibilities including serological artifact, new/different SRV, or an endogenous virus.
Topics: Animals; Betaretrovirus; Macaca; Monkey Diseases; Retroviridae Infections
PubMed: 28748661
DOI: 10.1111/jmp.12295 -
PLoS Pathogens Jun 2011The morphogenesis of retroviral particles is driven by Gag and GagPol proteins that provide the major structural component and enzymatic activities required for particle...
The morphogenesis of retroviral particles is driven by Gag and GagPol proteins that provide the major structural component and enzymatic activities required for particle assembly and maturation. In addition, a number of cellular proteins are found in retrovirus particles; some of these are important for viral replication, but many lack a known functional role. One such protein is clathrin, which is assumed to be passively incorporated into virions due to its abundance at the plasma membrane. We found that clathrin is not only exceptionally abundant in highly purified HIV-1 particles but is recruited with high specificity. In particular, the HIV-1 Pol protein was absolutely required for clathrin incorporation and point mutations in reverse transcriptase or integrase domains of Pol could abolish incorporation. Clathrin was also specifically incorporated into other retrovirus particles, including members of the lentivirus (simian immunodeficiency virus, SIVmac), gammaretrovirus (murine leukemia virus, MLV) and betaretrovirus (Mason-Pfizer monkey virus, M-PMV) genera. However, unlike HIV-1, these other retroviruses recruited clathrin primarily using peptide motifs in their respective Gag proteins that mimicked motifs found in cellular clathrin adaptors. Perturbation of clathrin incorporation into these retroviruses, via mutagenesis of viral proteins, siRNA based clathrin depletion or adaptor protein (AP180) induced clathrin sequestration, had a range of effects on the accuracy of particle morphogenesis. These effects varied according to which retrovirus was examined, and included Gag and/or Pol protein destabilization, inhibition of particle assembly and reduction in virion infectivity. For each retrovirus examined, clathrin incorporation appeared to be important for optimal replication. These data indicate that a number of retroviruses employ clathrin to facilitate the accurate morphogenesis of infectious particles. We propose a model in which clathrin contributes to the spatial organization of Gag and Pol proteins, and thereby regulates proteolytic processing of virion components during particle assembly.
Topics: Betaretrovirus; Cell Line; Clathrin; Gammaretrovirus; Gene Products, gag; Gene Products, pol; HIV-1; Humans; Lentivirus; Monomeric Clathrin Assembly Proteins; RNA Interference; RNA, Small Interfering; Virus Assembly
PubMed: 21738476
DOI: 10.1371/journal.ppat.1002119 -
Retrovirology Apr 2015Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary adenocarcinoma (OPA), a transmissible neoplastic disease of sheep. OPA is an economically...
BACKGROUND
Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary adenocarcinoma (OPA), a transmissible neoplastic disease of sheep. OPA is an economically important veterinary disease and is also a valuable naturally occurring animal model of human lung cancer, with which it shares a similar histological appearance and the activation of common cell signaling pathways. Interestingly, the JSRV Env protein is directly oncogenic and capable of driving cellular transformation in vivo and in vitro. Previous studies of JSRV infection in cell culture have been hindered by the lack of a permissive cell line for the virus. Here, we investigated the ability of JSRV to infect slices of ovine lung tissue cultured ex vivo.
RESULTS
We describe the use of precision cut lung slices from healthy sheep to study JSRV infection and transformation ex vivo. Following optimization of the culture system we characterized JSRV infection of lung slices and compared the phenotype of infected cells to natural field cases and to experimentally-induced OPA tumors from sheep. JSRV was able to infect cells within lung slices, to produce new infectious virions and induce cell proliferation. Immunohistochemical labeling revealed that infected lung slice cells express markers of type II pneumocytes and phosphorylated Akt and ERK1/2. These features closely resemble the phenotype of natural and experimentally-derived OPA in sheep, indicating that lung slice culture provides an authentic ex vivo model of OPA.
CONCLUSIONS
We conclude that we have established an ex vivo model of JSRV infection. This model will be valuable for future studies of JSRV replication and early events in oncogenesis and provides a novel platform for studies of JSRV-induced lung cancer.
Topics: Animals; Cell Proliferation; Jaagsiekte sheep retrovirus; Lung; Models, Theoretical; Organ Culture Techniques; Sheep, Domestic
PubMed: 25889156
DOI: 10.1186/s12977-015-0157-5