pinecone/core-2020-05-10-deduplication huggingface dataset:
Nucleolar Localization of Mouse Mammary Tumor Virus Proteins in T-Cell Lymphomas

AbstractTo characterize novel proteins expressed in lymphoma cells, monoclonal antibodies (MAbs) were raised against variant S49 mouse lymphoma cells. Immunoperoxidase analysis with a specific MAb, named M-66, revealed nuclear localization with prominent staining in the nucleoli of both tumorigenic (T-63) cells and nontumorigenic, immunogenic (T-25-Adh) cells. Weak signals were also observed in the cytoplasm and plasma membrane of both cells. Western blot analysis with M-66 antibody revealed a 14-kDa protein in nuclear extracts of both T-25-Adh and T-63 cells. An additional nuclear 21-kDa protein was evident only in T-63 cells. M-66 identified several clones from a T-25-Adh cDNA expression library. These clones demonstrated extensive homology (∼95% identity throughout their length) to the mouse mammary tumor virus (MMTV) env and LTR regions. Extensive amino acid sequence homology (∼90% identity) between the clones and the env protein was observed. M-66 identified the 14-kDa protein in another MMTV bearing T-cell lymphoma, EL-4. Immunoperoxidase analysis of EL-4 cells with M-66 also revealed prominent nucleolar staining. MMTV-negative cells and MMTV-positive cells of nonlymphocytic origin were devoid of both 14- and 21-kDa proteins. Moreover, an anti-MMTV gp52 (env) antibody precipitated the 21-kDa protein in T-63 cells. We thus suggest that MMTV bearing T-cell lymphomas express nucleolar proteins translated from the env region of MMTV
Suppression of Rat Bone Marrow Cells by Friend Murine Leukemia Virus Envelope Proteins

AbstractIn a retroviral rat model, we have investigated the nontransforming effects of murine leukemia virus FB29 on the bone marrow. Upon intraperitoneal inoculation with murine leukemia virus FB29 of either neonatal or adult rats, bone marrow cells became massively infected within the first 12 days postinoculation. In neonatally inoculated rats, a persistent productive bone marrow infection was established, whereas in rats inoculated as adults, no infected bone marrow cells could be detected beyond 12 days postinoculation. Retroviral infection was most likely cleared by an antiviral immune response (Heinet al.,1995,Virology211, 408–417). Exposure to virus irreversibly decreased numbers of bone marrow cells staining with monoclonal antibody OX7 by 10–30%. Reduction of OX7+bone marrow cells by 20% was also observedin vitro,after bone marrow cells from uninfected adult rats had been co-incubated with virus. FB29-envelope proteins were sufficient alone to reduce numbers of OX7+bone marrow cells, bothin vivoandin vitro.According to results on incorporation of propidium iodide, decreased numbers of OX7+cells were due to cell death. By flow cytometric analyses OX7+bone marrow cells as well as monocytes/macrophages were identified to be major target cells for infection with FB29 within the bone marrow. Thus, the mechanism(s) responsible for death of OX7+bone marrow cells might be due to direct toxicity of viral envelope proteins and/or to interactions of viral envelope proteins with cells of the monocytic lineage
Novel Structures of Two Virus-like RNA Elements from a Diseased Isolate of the Dutch Elm Disease Fungus,Ophiostoma novo-ulmi

AbstractThe nucleotide sequences of 2 of the 10 mitochondrial double-stranded (ds) RNA segments in a diseased isolate, Log1/3-8d2(Ld), ofOphiostoma novo-ulmi,RNA-7 (1057 nucleotides) and RNA-10 (317–330 nucleotides), have been determined. Both RNAs are A-U-rich, but in Southern and Northern blots, no hybridization with mitochondrial DNA or RNA could be detected. Only very short open reading frames were found in both RNAs. As most of its sequence is unrelated to any of the other Ld dsRNAs, RNA-7 may be regarded as a satellite RNA. Northern blotting detected a full-length single-stranded (ss) form of RNA-7 in nucleic acid extracts from Ld. The 5′- and 3′-terminal 39 nucleotides of ssRNA-7 are imperfect inverted complementary repeats of each other, which could cause ssRNA-7 to form a panhandle structure. In addition, the 5′-terminal nucleotides 1–28 and 3′-terminal nucleotides 1032–1057 of ssRNA-7 each contained inverted complementary sequences, allowing the possibility for each terminus to form separate stem-loop structures. The combination of these two structural features has not been found previously in any dsRNA or ssRNA virus. RNA-10 was shown to have an unusual structure, consisting of a mosaic of sequences derived from regions of the 5′- and 3′-termini, or just the 5′-terminus, of RNA-7. RNA-10 has a high degree of inverted complementarity, with the potential to be folded into a very stable hairpin structure. A model for the formation of RNA-10 is presented, involving replicase-driven strand switching between (−)-strand and (+)-strand templates during RNA synthesis, followed by utilization of the nascent strand as a primer and template to form a snap-back RNA
Characterization of the Brome Mosaic Virus Movement Protein Expressed inE. coli

AbstractThe biochemical and functional properties of the movement protein (MP) of brome mosaic virus (BMV) were investigated. Expression and purification of the BMV MP fromEscherichia coliresulted in a pure and soluble protein preparation. Sucrose gradient centrifugation revealed that BMV MP forms oligomers consisting of two or more copies but no higher order multimers even when different ionic strengths and pHs were applied. Nitro-cellulose filter binding and gel retardation studies showed thatin vitrothe BMV MP preferentially bound to ss nucleic acids (RNA and DNA); the affinity to ssRNA was lower compared to BMV coat protein. The binding to ss nucleic acid was cooperative and not sequence specific and the hypothetical binding site was calculated to be around three to six nucleotides per MP monomer. The nucleic acid binding properties of the BMV MP are discussed in relation to the recent finding that this protein is also able to form tubular structures in infected protoplasts
Chemokine Homolog of Molluscum Contagiosum Virus: Sequence Conservation and Expression

AbstractAn analysis of the complete Molluscum contagiosum virus (MCV-1) genome sequence revealed a 104-amino-acid open reading frame (MC148R) that is structurally related to the β (CC) family of chemokines. The predicted MCV chemokine homolog (MCCH) has a deletion in the NH2-terminal activation domain, suggesting the absence of chemoattractant activity. The principal objectives of the present study were to determine whether: (i) MCCH is conserved in independent isolates of MCV-1 and MCV-2; (ii) MCCH mRNA is expressedin vivo;and (iii) the MCCH protein is secreted from mammalian cells. The nucleotide sequence of the MCCH gene locus was determined for 27 isolates of MCV-1 and 2 of MCV-2 obtained from 29 MCV-infected individuals. In each case, the characteristic CC sequence, the NH2-terminal deletion, and the length of the open reading frame were conserved, although there were some, mostly conservative, amino acid substitutions. Since MCV cannot be propagated in cell culture, mRNA was synthesizedin vitroby the early transcription apparatus in purified MCV virions. MCCH RNA was amplified by RT–PCR; the sequence included the complete open reading frame and extended 40 to 50 nucleotides past the first poxviral termination signal (TTTTTNT). Similar RT–PCR results were obtained using total cellular RNA derived from MCV-infected tissue specimens. Finally, the MCCH open reading frame was expressed in a vaccinia virus vector and the predicted size polypeptide was secreted into the medium, as determined by Western blotting. Taken together, our data support the prediction that MCV expresses a secreted chemokine homolog that could antagonize the inflammatory responsein vivo
The Antiviral Action of Interferon Is Potentiated by Removal of the Conserved IRTAM Domain of the IFNAR1 Chain of the Interferon α/β Receptor: Effects on JAK-STAT Activation and Receptor Down-regulation

The first cloned chain (IFNAR1) of the human interferon-α (IFNα) receptor acts as a species-specific transducer for type I IFN action when transfected into heterologous mouse cells. Stably transfected mouse L929 cell lines expressing truncation mutants of the intracellular domain of the human IFNAR1 chain were tested for biological responses to human IFNα. Deletion of the intracellular domain resulted in a complete loss of sensitivity to the biological activity of human IFN but markedly increased IFNAR1 cell surface expression, demonstrating that the intracellular domain is required for biological function and contains a domain that negatively regulates its cell surface expression. Removal of the conserved membrane distal 16-amino-acid IRTAM (InterferonReceptorTyrosineActivationMotif) sequence: (1) increased sensitivity to IFNα's antiviral activity, (2) increased the rapid IFNα-dependent formation of STAT-containing DNA-binding complexes, (3) prolonged tyrosine phosphorylation kinetics of the JAK-STAT pathway, and (4) blocked the IFN-dependent down-regulation of the IFNAR1 chain. These results indicate that the IRTAM negatively regulates signaling events required for the induction of IFN's biological actions via regulating receptor down-regulation
Phosphorylation of DHBV Pre-S: Identification of the Major Site of Phosphorylation and Effects of Mutations on the Virus Life Cycle

AbstractFour potential serine/threonine phosphorylation sites [(S/T)-P motif], designated P1–P4, on the pre-S protein of duck hepatitis B virus (DHBV) have been mutated. Mutants include single (P2, P3, P4) and double amino acid substitutions (P1+P2, P3+P4) and one with all four sites mutated (4P). Serine at position 118 (P3) was identified as the major site of phosphorylation by Western blotting and radioimmunoprecipitation afterin vitrocell labeling with [35S]methionine or [33P]orthophosphate. Mutant virions generated by transfection of LMH cells were infectious bothin vitroin duck hepatocyte primary cultures andin vivoin Pekin ducks. Intracellular relaxed circular (RC) and covalently closed circular (ccc) DNA syntheses were not affected by the P3 mutation or even the quadruple mutant. Extracellular virus production was slightly increased when the P3 site was mutated. CsCl gradient centrifugation showed no clear difference between mutant and wild-type virus with respect to the ratios of enveloped virus and nucleocapsid particles in hepatocyte culture supernatants. Trypsin or V8 protease digestion with or without NP-40 indicated that phosphorylation of the pre-S domain is not involved in determining the transmembrane topology of DHBV large protein. This phenotypic analysis indicates that DHBV pre-S phosphorylation has no apparent effect on DHBV replication and formation of mature viral particles in duck hepatocyte primary culture and does not affect infectivity in ducklings
Capsids Are Formed in a Mutant Virus Blocked at the Maturation Site of the UL26 and UL26.5 Open Reading Frames of Herpes Simplex Virus Type 1 but Are Not Formed in a Null Mutant of UL38 (VP19C)

AbstractPreviously we reported that null mutant viruses of UL19 (VP5) or of UL18 (VP23), essential components of herpes simplex virus type 1 (HSV-1) capsid shells, do not form precursor capsid structures as judged by sedimentation and electron microscope analysis. A goal of the present experiments was to isolate a null mutant virus for the remaining essential component of capsid shells, VP19C, encoded by the UL38 open reading frame (ORF). Furthermore, we wished to determine if a virus altered in the UL26 maturation cleavage site at residues 610 and 611 produced a lethal phenotype. Therefore, we decided to isolate cell lines that encode and express multiple capsid genes. Several cell lines were isolated by transformation of Vero cells and one designated C32 expressed all of the essential capsid proteins. Using this cell line we isolated a null mutant virus in the UL38 ORF and a mutant virus that was altered at residues 610 and 611 of the UL26 and UL26.5 gene products. We found that the null mutant in VP19C did not form a detectable product as judged by sedimentation and electron microscope analyses following infection of nonpermissive cells. The mutant virus altered at the UL26 maturation site resulted in the accumulation of B capsids. Therefore, cleavage at this site was essential for the maturation of B capsids into C capsids. Interestingly, the absence of cleavage at the maturation site was required for the retention of VP24 in the capsid
The Herpes Simplex Virus Immediate-Early Protein ICP27 Shuttles between Nucleus and Cytoplasm

AbstractICP27 is an essential herpes simplex virus type 1 (HSV-1) nuclear protein which regulates viral early and late genes during infection. The exact mechanism by which ICP27 modulates viral gene expression is unknown, but considerable evidence suggests that it functions posttranscriptionally. In this study, we have asked whether ICP27, like some other viral and cellular posttranscriptional regulatory proteins, shuttles between the nuclear and cytoplasmic compartments of the cell. Using an interspecies heterokaryon assay, we demonstrate that ICP27, but not the HSV-1 nuclear proteins ICP4 or ICP8, is an efficient shuttling protein. ICP27's shuttling ability does not depend on viral infection or other HSV-1 proteins, as it shuttles even when transiently expressed in uninfected cells. To understand the importance of shuttling for ICP27's regulatory functions, we examined several mutant forms of ICP27 to see whether they exhibited altered shuttling. We identified three ICP27 mutations which partially disrupt shuttling, as well as one mutation, M15, which completely abrogates this activity. The M15 mutation alters residues 465 and 466 near the carboxyl terminus of ICP27 and was previously shown to inactivate ICP27's ability to induce certain viral late mRNAs. These results suggest that ICP27's nuclear shuttling activity is involved in its viral late gene activation function
Differential Behavior of the Mo+PyF101 Enhancer Variant of Moloney Murine Leukemia Virus in Rats and Mice

AbstractThe Mo+PyF101 enhancer variant of Moloney murine leukemia virus (M-MuLV) has been very useful in investigating M-MuLV leukemogenesis. When inoculated subcutaneously (sc) into neonatal mice, Mo+PyF101 M-MuLV is attenuated for development of disease. Previous studies in mice infected with wild-type M-MuLV have revealed several important preleukemic events, including development of splenic hyperplasia, defects in bone marrow hematopoiesis, andin vivogeneration of MCF viruses that arise by recombination in the uninfected mouse. Mo+PyF101 M-MuLV is defective in inducing these effects after sc inoculation. In the experiments reported here, a study of Mo+PyF101 M-MuLV infection in rats was carried out. Wild-type M-MuLV is leukemogenic in rats, but infected rats do not form MCF recombinants since they lack the necessary endogenous polytropic envelope sequences. Since Mo+PyF101 M-MuLV's leukemogenic defect is correlated with a failure to generate MCF recombinants, it seemed possible that wild-type M-MuLV might not have a leukemogenic advantage over Mo+PyF101 M-MuLV in rats, where MCF recombinants cannot form. Neonatal Fisher F344 rats were inoculated sc or intraperitoneally by wild-type and Mo+PyF101 M-MuLVs. Surprisingly, Mo+PyF101 M-MuLV was completely deficient in leukemogenesis in rats when inoculated by either route while wild-type M-MuLV induced lymphoma with the predicted time course. The leukemogenic defect for Mo+PyF101 M-MuLV resulted from a pronounced defect for establishing infection in rats. Further studies of wild-type M-MuLV in rats indicated that infection was confined almost exclusively to the thymus at early times. In mice wild-type M-MuLV establishes substantial infection in other hematopoietic organs such as spleen and bone marrow as well. Thymic infection was also correlated with a decrease in thymic cellularity at early times
The Host Range and Interference Properties of Two Closely Related Feline Leukemia Variants Suggest That They Use Distinct Receptors

AbstractThe proviral clones 61E and 61C represent two closely related variants of feline leukemia virus (FeLV) that exhibit significant differences in their biological and pathogenic properties. The major pathogenic determinant has been mapped to the extracellular envelope glycoprotein (Env-SU), but the mechanism by which envelope differences influence pathogenesis is not well understood. Moreover, it is unclear whether these viruses infect the same target cells and/or enter cells using the same receptor. In the present study, we exploited a recently developed single cycle infection assay to examine the host range and interference properties of 61E and 61C FeLVs and found that these two FeLV variants differ significantly in their host ranges and receptor usages. FeLV-61C was found to be an ecotropic virus; the entry of viruses bearing a 61C envelope protein (Env-SU) into cell lines was limited to feline T-cells and feline fibroblasts. In contrast, the host range of 61E includes, in addition to all feline cells examined, some canine, murine, and human cell lines. Feline fibroblast and feline T-cells that expressed 61E envelope were resistant to infection with a virus bearing a 61E Env-SU, whereas these same cells were susceptible to infection by an otherwise similar virus pseudotyped with the 61C Env-SU. This pattern of interference was observed in cells expressing 61E envelope alone, in the absence of other FeLV gene products, demonstrating that interference was mediated specifically by Env-SU. Fibroblast cells chronically infected with a 61C virus were partially resistant to infection with a virus having a 61C Env-SU, but were not resistant to infection by a virus having a 61E Env-SU. On the basis of the current understanding of virus–receptor interactions, the lack of interference between 61E and 61C under conditions where there is significant homologous interference, combined with the differences in their host cell range, leads us to conclude that 61E and 61C use two distinct primary cellular receptors for entry
Molecular Epidemiology of HTLV-II among United States Blood Donors and Intravenous Drug Users: An Age–Cohort Effect for HTLV-II RFLP Type a0

AbstractMolecular subtyping was used to investigate the epidemiology of human T-lymphotropic virus type II (HTLV-II) in the United States. Nested polymerase chain reaction of the HTLV-II long terminal repeat region followed by restriction fragment length polymorphism (RFLP) analysis was performed on HTLV-II seropositive subjects including 97 U.S. blood donors without major risk factors for HTLV-II infection, 53 injection drug users (IDU), and 10 American Indian blood donors. Three new HTLV-II RFLP types were confirmed with DNA sequencing and phylogenetic analysis. HTLV-II RFLP type a0 (Switzer classification) was associated with older age [adjusted odds ratio (OR) 1.06 per year of age, 95% confidence interval (CI) 1.02–1.09] and with Black (OR 5.24, 95% CI 1.90–14.47) and White (OR 4.43, 95% CI 1.67–11.75) race/ ethnicity. These data are consistent with an age–cohort effect for HTLV-II RFLP type a0 among older White and Black IDU and blood donors. This finding could be explained by an epidemic of non-a0 HTLV-II RFLP types among younger persons of Hispanic and other race/ethnicity, superimposed upon endemic HTLV-II RFLP type a0 among older Black and White persons
Processing of the Coronavirus MHV-JHM Polymerase Polyprotein: Identification of Precursors and Proteolytic Products Spanning 400 Kilodaltons of ORF1a

AbstractThe replicase of mouse hepatitis virus strain JHM (MHV-JHM) is encoded by two overlapping open reading frames, ORF1a and ORF1b, which are translated to produce a 750-kDa precursor polyprotein. The polyprotein is proposed to be processed by viral proteinases to generate the functional replicase complex. To date, only the MHV-JHM amino-terminal proteins p28 and p72, which is processed to p65, have been identified. To further elucidate the biogenesis of the MHV-JHM replicase, we cloned and expressed five regions of ORF1a in bacteria and prepared rabbit antisera to each region. Using the immune sera to immunoprecipitate radiolabeled proteins from MHV-JHM infected cells, we determined that the MHV-JHM ORF1a is initially processed to generate p28, p72, p250, and p150. Pulse–chase analysis revealed that these intermediates are further processed to generate p65, p210, p40, p27, the MHV 3C-like proteinase, and p15. A putative replicase complex consisting of p250, p210, p40, p150, and a large protein (>300 kDa) coprecipitate from infected cells disrupted with NP-40, indicating that these proteins are closely associated even after initial proteolytic processing. Immunofluorescence studies revealed punctate labeling of ORF1a proteins in the perinuclear region of infected cells, consistent with a membrane-association of the replicase complex. Furthermore,in vitrotranscription/translation studies of the MHV-JHM 3Cpro and flanking hydrophobic domains confirm that 3C protease activity is significantly enhanced in the presence of canine microsomal membranes. Overall, our results demonstrate that the MHV-JHM ORF1a polyprotein: (1) is processed into more than 10 protein intermediates and products, (2) requires membranes for efficient biogenesis, and (3) is detected in discrete membranous regions in the cytoplasm of infected cells
Type Specific and Genotype Cross Reactive B Epitopes of the L1 Protein of HPV16 Defined by a Panel of Monoclonal Antibodies

AbstractMouse monoclonal antibodies (mAbs) were raised against the major capsid protein, L1, of human papillomavirus type 16 (HPV16), produced inEscherichia coliwith the expression plasmid pTrcL1. Epitope specificity could be assigned to 11 of these 12 antibodies using a series of linear peptides and fusion proteins from HPV16. One mAb (MC53) recognized a novel linear epitope that appears to be unique to the HPV16 genotype. A further 11 mAbs were characterized as recognizing novel and previously defined linear and conformational epitopes shared among more than one HPV genotype. The apparently genotype specific mAb could be useful for the development of diagnostic tests for vegetative virus infection in clinical specimens
Importance of the Herpes Simplex VirusUL24Gene for Productive Ganglionic Infection in Mice

AbstractTheUL24gene of herpes simplex virus overlaps the viral thymidine kinase (tk) gene. Most previous studies ofUL24have examinedUL24mutants that have also containedtkand sometimes other mutations. To address the importance ofUL24for viral replication in cell culture and in infections of a mammalian host, we constructed a mutant virus containing aUL24nonsense mutation that does not affect TK activity and a second mutant that contains clustered point mutations inUL24and a mutation intkthat does not by itself affect the ability of the virus to replicate acutely in mouse ganglia or to reactivate from latent infection following corneal inoculation of mice. Both mutant viruses replicated in cells in culture and in the mouse eye, albeit less efficiently than wild type or control viruses. Both mutants were much more severely impaired for acute replication in trigeminal ganglia and for reactivation from latency following explant of these ganglia. Viral DNA and latency-associated transcripts were present, albeit at lower levels in ganglia infected with the nonsense mutant. These results indicate thatUL24is especially important for productive infection of mouse sensory ganglia and may have implications for the behaviors of certaintkmutants in pathogenesis