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Journal of Virology Oct 1981The new avian retroviruses UR1 and UR2 were isolated from spontaneous tumors of chickens by cocultivation of tumor material with susceptible chicken embryo fibroblasts....
The new avian retroviruses UR1 and UR2 were isolated from spontaneous tumors of chickens by cocultivation of tumor material with susceptible chicken embryo fibroblasts. In vitro, UR1 induced formation of small foci of round and fusiform cells. On the other hand, cells infected by UR2 assumed an extremely elongated morphology. In vivo, both viruses induced fibrosarcomas and myxosarcomas with short latencies. Infectivity assays with and without mitomycin C showed that both viruses were defective for replication, but transformed nonproducing cell clones were obtained only with UR1. UR1-infected transformed nonproducing clones did not release particles detectable by reverse transcriptase assays, and fusion of transformed nonproducing cells with quail cells chronically infected with Rous sarcoma virus (a Bryan strain) failed to rescue infectious virus. This suggested that UR1 does not code for functional envelope glycoproteins. In this regard, UR1 appeared to be similar to Fujinami, PRCII, and Y73 viruses. The helper viruses of partially purified stocks of UR1 and UR2 appeared to belong to subgroup A, but these helper viruses were distinguishable from each other, as shown by host range experiments and neutralization tests. Hybridization studies with DNA complementary to the src gene of Rous sarcoma virus and RNAs extracted from both UR1 and UR2 showed no homology between the genomes of the new isolates and the transforming gene of Rous sarcoma virus.
Topics: Alpharetrovirus; Animals; Base Sequence; Cell Transformation, Viral; Chickens; Defective Viruses; RNA, Viral
PubMed: 6270379
DOI: 10.1128/JVI.40.1.268-275.1981 -
Viruses Apr 2018In recent years, cases of avian leukosis virus (ALV) infection have become more frequent in China. We isolated 6 ALV strains from yellow feather broiler breeders in...
In recent years, cases of avian leukosis virus (ALV) infection have become more frequent in China. We isolated 6 ALV strains from yellow feather broiler breeders in south China from 2014 to 2016. Their full genomes were sequenced, compared, and analyzed with other reference strains of ALV. The complete genomic nucleotide sequences of GD150509, GD160403, GD160607, GDFX0601, and GDFX0602 were 7482 bp in length, whereas GDFX0603 was 7480 bp. They shared 99.7% to 99.8% identity with each other. Homology analysis showed that the , , long terminal repeats (LTRs), and the transmembrane region (gp37) of the genes of the 6 viruses were well conserved to endogenous counterpart sequences (>97.8%). However, the gp85 genes displayed high variability with any known chicken ALV strains. Growth kinetics of DF-1 cells infected with the isolated ALV showed viral titers that were lower than those infected with the GD13 (ALV-A), CD08 (ALV-B), and CHN06 (ALV-J) on day 7 post-infection. The infected Specific-pathogen-free (SPF) chickens could produce continuous viremia, atrophy of immune organs, growth retardation and no tumors were observed. These subgroup ALVs are unique and may be common in south China. The results suggested that updating the control and eradication program of exogenous ALV for yellow feather broiler breeders in south China needs to be considered because of the emergence of the new subgroup viruses.
Topics: Animals; Avian Leukosis; Avian Leukosis Virus; Chickens; China; Genetic Variation; Genome, Viral; Phylogeny; Recombination, Genetic; Sequence Homology; Terminal Repeat Sequences; Viral Proteins; Whole Genome Sequencing
PubMed: 29652854
DOI: 10.3390/v10040194 -
Molecular Therapy : the Journal of the... May 2012Comparative integrome analyses have highlighted alpharetroviral vectors with a relatively neutral, and thus favorable, integration spectrum. However, previous studies...
Comparative integrome analyses have highlighted alpharetroviral vectors with a relatively neutral, and thus favorable, integration spectrum. However, previous studies used alpharetroviral vectors harboring viral coding sequences and intact long-terminal repeats (LTRs). We recently developed self-inactivating (SIN) alpharetroviral vectors with an advanced split-packaging design. In a murine bone marrow (BM) transplantation model we now compared alpharetroviral, gammaretroviral, and lentiviral SIN vectors and showed that all vectors transduced hematopoietic stem cells (HSCs), leading to comparable, sustained multilineage transgene expression in primary and secondary transplanted mice. Alpharetroviral integrations were decreased near transcription start sites, CpG islands, and potential cancer genes compared with gammaretroviral, and decreased in genes compared with lentiviral integrations. Analyzing the transcriptome and intragenic integrations in engrafting cells, we observed stronger correlations between in-gene integration targeting and transcriptional activity for gammaretroviral and lentiviral vectors than for alpharetroviral vectors. Importantly, the relatively "extragenic" alpharetroviral integration pattern still supported long-term transgene expression upon serial transplantation. Furthermore, sensitive genotoxicity studies revealed a decreased immortalization incidence compared with gammaretroviral and lentiviral SIN vectors. We conclude that alpharetroviral SIN vectors have a favorable integration pattern which lowers the risk of insertional mutagenesis while supporting long-term transgene expression in the progeny of transplanted HSCs.
Topics: Alpharetrovirus; Animals; Cell Line; CpG Islands; Gammaretrovirus; Gene Targeting; Genetic Vectors; Hematopoietic Stem Cell Transplantation; Hematopoietic Stem Cells; Humans; Lentivirus; Mice; Mutagenesis, Insertional; Risk Factors; Terminal Repeat Sequences; Transcription Initiation Site; Transcriptome; Transduction, Genetic; Transgenes
PubMed: 22334016
DOI: 10.1038/mt.2011.309 -
Structure (London, England : 1993) Jun 2000The capsid protein (CA) of retroviruses, such as Rous sarcoma virus (RSV), consists of two independently folded domains. CA functions as part of a polyprotein during...
BACKGROUND
The capsid protein (CA) of retroviruses, such as Rous sarcoma virus (RSV), consists of two independently folded domains. CA functions as part of a polyprotein during particle assembly and budding and, in addition, forms a shell encapsidating the genomic RNA in the mature, infectious virus.
RESULTS
The structures of the N- and C-terminal domains of RSV CA have been determined by X-ray crystallography and solution nuclear magnetic resonance (NMR) spectroscopy, respectively. The N-terminal domain comprises seven alpha helices and a short beta hairpin at the N terminus. The N-terminal domain associates through a small, tightly packed, twofold symmetric interface within the crystal, different from those previously described for other retroviral CAs. The C-terminal domain is a compact bundle of four alpha helices, although the last few residues are disordered. In dilute solution, RSV CA is predominantly monomeric. We show, however, using electron microscopy, that intact RSV CA can assemble in vitro to form both tubular structures constructed from toroidal oligomers and planar monolayers. Both modes of assembly occur under similar solution conditions, and both sheets and tubes exhibit long-range order.
CONCLUSIONS
The tertiary structure of CA is conserved across the major retroviral genera, yet sequence variations are sufficient to cause change in associative behavior. CA forms the exterior shell of the viral core in all mature retroviruses. However, the core morphology differs between viruses. Consistent with this observation, we find that the capsid proteins of RSV and human immunodeficiency virus type 1 exhibit different associative behavior in dilute solution and assemble in vitro into different structures.
Topics: Avian Sarcoma Viruses; Capsid; Crystallography, X-Ray; Humans; Magnetic Resonance Spectroscopy; Microscopy, Electron; Models, Molecular; Protein Structure, Secondary; Protein Structure, Tertiary
PubMed: 10873863
DOI: 10.1016/s0969-2126(00)00148-9 -
Fukushima Journal of Medical Science Dec 2004Rous sarcoma virus (RSV)-derived retroviral vectors have allowed for efficient gene transfer into the chicken embryo which is a classical model for studying vertebrate... (Review)
Review
Rous sarcoma virus (RSV)-derived retroviral vectors have allowed for efficient gene transfer into the chicken embryo which is a classical model for studying vertebrate development. Current evidence reveals that this method can be used for regionally restricted expression, inducible expression, and for interfering with endogenous gene function, suggesting that gain-of-function and loss-of-function strategies for specific genes can be achieved spatially and temporally in the avian embryo. Thus, retroviral-mediated gene transfer into the chicken embryo coupled with a wide variety of strategies is now an important tool to address specific biological questions in the vertebrate.
Topics: Animals; Animals, Genetically Modified; Avian Sarcoma Viruses; Chick Embryo; Gene Expression; Gene Silencing; Gene Transfer Techniques; Genetic Vectors; Virus Replication
PubMed: 15779569
DOI: 10.5387/fms.50.37 -
Proceedings of the National Academy of... Apr 1976Cocultivation of cells derived from embryos of golden pheasants or Amherst pheasants with chicken embryo cells infected with Bryan strain of Rous sarcoma virus resulted... (Comparative Study)
Comparative Study
Cocultivation of cells derived from embryos of golden pheasants or Amherst pheasants with chicken embryo cells infected with Bryan strain of Rous sarcoma virus resulted in the detection of viruses which appear to be endogenous in these pheasant cells. The pheasant viruses (PV) were similar to avian leukosis-sarcoma viruses (ALSV) in their gross morphology, in the size of their RNA, in the presence of a virion-associated RNA-dependent DNA polymerase (DNA nucleotidyltransferase; deoxynucleoside triphosphate: DNA deoxynucleotidyltransferase; EC 2.7.7.7), and in their growth characteristics. PV also serves as a helper for the glycoprotein-defective Rous sarcoma virus. However, PV was shown to be different from both ALSV and reticuloendotheliosis virus in the following properties: (i) PV does not have ALSV group specific antigens; (ii) the protein composition of PV is different from those of the other two groups of viruses; (iii) PV fails to complement the defective polymerase of alpha type Rous sarcoma virus; and (iv) PV RNA shows no detectable homology with nucleic acids of the other two groups of viruses. Thus, PV appears to be a new class of RNA viruses which contain RNA-dependent DNA polymerase.
Topics: Alpharetrovirus; Animals; Antigens, Viral; Birds; DNA, Viral; Glycoproteins; Helper Viruses; Inclusion Bodies, Viral; Oncogenic Viruses; Peptides; RNA Viruses; RNA, Viral; RNA-Directed DNA Polymerase; Reticuloendotheliosis virus; Viral Proteins
PubMed: 57621
DOI: 10.1073/pnas.73.4.1333 -
Journal of Virology Apr 1980Avian erythroblastosis virus (AEV) RNA rescued from nonproducer cells by superinfection with a helper virus is translated into three polypeptides in the...
Avian erythroblastosis virus (AEV) RNA rescued from nonproducer cells by superinfection with a helper virus is translated into three polypeptides in the messenger-dependent rabbit reticulocyte lysate. A 75,000 molecular weight polypeptide (P75AEV) is synthesized from 28S RNA and is encoded by the 5' section of the AEV RNA, including gag-related and AEV-specific sequences. The P75AEV synthesized in infected cells and the P75AEV synthesized in the cell-free system are electrophoretically identical. A 44,000 molecular weight polypeptide (P44AEV) is synthesized from 20-24S RNA, apparently from the 3' section of the AEV-specific RNA sequence. A minor 37,000 molecular weight polypeptide (P37AEV) is synthesized from 20S AEV RNA. A comparison is drawn between the cell-free products of MC29 and AEV RNAs.
Topics: Alpharetrovirus; Avian Leukosis Virus; Cell-Free System; Genes, Viral; Molecular Weight; Protein Biosynthesis; RNA, Viral; Viral Proteins
PubMed: 6246260
DOI: 10.1128/JVI.34.1.280-284.1980 -
Viruses May 2019The subgroup A through E avian sarcoma and leukosis viruses ASLV(A) through ASLV(E) are a group of highly related alpharetroviruses that have evolved to use very...
Mutations in Both the Surface and Transmembrane Envelope Glycoproteins of the RAV-2 Subgroup B Avian Sarcoma and Leukosis Virus Are Required to Escape the Antiviral Effect of a Secreted Form of the Tvb Receptor †.
The subgroup A through E avian sarcoma and leukosis viruses ASLV(A) through ASLV(E) are a group of highly related alpharetroviruses that have evolved to use very different host protein families as receptors. We have exploited genetic selection strategies to force the replication-competent ASLVs to naturally evolve and acquire mutations to escape the pressure on virus entry and yield a functional replicating virus. In this study, evolutionary pressure was exerted on ASLV(B) virus entry and replication using a secreted for of its Tvb receptor. As expected, mutations in the ASLV(B) surface glycoprotein hypervariable regions were selected that knocked out the ability for the mutant glycoprotein to bind the sTvb-IgG inhibitor. However, the subgroup B Rous associated virus 2 (RAV-2) also required additional mutations in the C-terminal end of the SU glycoprotein and multiple regions of TM highlighting the importance of the entire viral envelope glycoprotein trimer structure to mediate the entry process efficiently. These mutations altered the normal two-step ASLV membrane fusion process to enable infection.
Topics: Animals; Avian Leukosis Virus; Avian Sarcoma Viruses; Cell Line; Chick Embryo; Chickens; Mutation; Receptors, Virus; Viral Envelope Proteins; Virus Replication
PubMed: 31159208
DOI: 10.3390/v11060500 -
Journal of Virology Nov 2012Programmed -1 ribosomal frameshifting is widely used in the expression of RNA virus replicases and represents a potential target for antiviral intervention. There is...
Programmed -1 ribosomal frameshifting is widely used in the expression of RNA virus replicases and represents a potential target for antiviral intervention. There is interest in determining the extent to which frameshifting efficiency can be modulated before virus replication is compromised, and we have addressed this question using the alpharetrovirus Rous sarcoma virus (RSV) as a model system. In RSV, frameshifting is essential in the production of the Gag-Pol polyprotein from the overlapping gag and pol coding sequences. The frameshift signal is composed of two elements, a heptanucleotide slippery sequence and, just downstream, a stimulatory RNA structure that has been proposed to be an RNA pseudoknot. Point mutations were introduced into the frameshift signal of an infectious RSV clone, and virus replication was monitored following transfection and subsequent infection of susceptible cells. The introduced mutations were designed to generate a range of frameshifting efficiencies, yet with minimal impact on encoded amino acids. Our results reveal that point mutations leading to a 3-fold decrease in frameshifting efficiency noticeably reduce virus replication and that further reduction is severely inhibitory. In contrast, a 3-fold stimulation of frameshifting is well tolerated. These observations suggest that small-molecule inhibitors of frameshifting are likely to have potential as agents for antiviral intervention. During the course of this work, we were able to confirm, for the first time in vivo, that the RSV stimulatory RNA is indeed an RNA pseudoknot but that the pseudoknot per se is not absolutely required for virus viability.
Topics: Base Sequence; Frameshifting, Ribosomal; Gene Products, gag; Gene Products, pol; Nucleic Acid Conformation; Point Mutation; RNA, Viral; Rous sarcoma virus; Virus Replication
PubMed: 22896611
DOI: 10.1128/JVI.01846-12 -
Journal of Virology Nov 2010The assembly of retroviruses is driven by oligomerization of the Gag polyprotein. We have used cryo-electron tomography together with subtomogram averaging to describe... (Comparative Study)
Comparative Study
The assembly of retroviruses is driven by oligomerization of the Gag polyprotein. We have used cryo-electron tomography together with subtomogram averaging to describe the three-dimensional structure of in vitro-assembled Gag particles from human immunodeficiency virus, Mason-Pfizer monkey virus, and Rous sarcoma virus. These represent three different retroviral genera: the lentiviruses, betaretroviruses and alpharetroviruses. Comparison of the three structures reveals the features of the supramolecular organization of Gag that are conserved between genera and therefore reflect general principles of Gag-Gag interactions and the features that are specific to certain genera. All three Gag proteins assemble to form approximately spherical hexameric lattices with irregular defects. In all three genera, the N-terminal domain of CA is arranged in hexameric rings around large holes. Where the rings meet, 2-fold densities, assigned to the C-terminal domain of CA, extend between adjacent rings, and link together at the 6-fold symmetry axis with a density, which extends toward the center of the particle into the nucleic acid layer. Although this general arrangement is conserved, differences can be seen throughout the CA and spacer peptide regions. These differences can be related to sequence differences among the genera. We conclude that the arrangement of the structural domains of CA is well conserved across genera, whereas the relationship between CA, the spacer peptide region, and the nucleic acid is more specific to each genus.
Topics: Amino Acid Sequence; Cell Line; Conserved Sequence; Gene Products, gag; HIV-1; Humans; Mason-Pfizer monkey virus; Molecular Sequence Data; Protein Structure, Tertiary; Rous sarcoma virus; Sequence Alignment; Virion; Virus Assembly
PubMed: 20810738
DOI: 10.1128/JVI.01423-10