pinecone/core-2020-05-10-deduplication huggingface dataset:
The Carboxy-Terminal p3GagDomain of the Human Foamy Virus Gag Precursor Is Required for Efficient Virus Infectivity

AbstractProteolytic processing of foamy virus Gag proteins appears to be different from that of other retroviruses. A single carboxy-terminal cleavage site is consistently detectable in human foamy virus (HFV) Gag precursor protein p74Gagderived from infected cells and/or purified virus particles. Using a recombinant HFV protease, we have determined the p74Gagcleavage site that results in p70Gagand the carboxy-terminal p3Gag(Pfrepperet al.,1997,Biochem. Biophys. Res. Commun.237, 548–553). To study the biological functions of p3Gag, proviral DNA clones were constructed coding for a carboxy-terminally truncated p70Gaglacking the entire p3Gagprotein. Removal of p3Gagresulted in an about 100-fold lower virus titer. The expression of other HFV proteins and the processing of Pol proteins were indistinguishable from those of wild-type-transfected cells. The defect in viral infectivity of the p3 mutants was partially restored by coexpressing the full-length p74Gagproteinin trans.The deletion of p3Gagresulted in particle assembly with wild-type virion morphology and encapsidation of Pol proteins. Our data show that the carboxy-terminal p3Gagprotein has an important function for viral infectivity but is not required for preassembly of capsids, virus morphogenesis, and incorporation of Pol proteins into virions
A Baculovirus Single-Stranded DNA Binding Protein, LEF-3, Mediates the Nuclear Localization of the Putative Helicase P143

AbstractThe intracellular localization of the baculovirusAutographa californicanuclear polyhedrosis virusp143gene product (P143) was investigated by immunofluoresence staining of infected and transfected cells. As expected for a protein essential for viral DNA replication, under these conditions, P143 was localized to the nucleus. However, when a plasmid directing the synthesis of P143 from its own promoter was co-transfected with a plasmid expressing IE-1, P143 was found in the cytoplasm. Cotransfection of cells with a series of plasmids expressing viral genes sufficient for stimulation of plasmid replication resulted in nuclear localization of P143 suggesting that one of the gene products required for viral DNA replication may also assist nuclear localization of P143. Sequential deletion of various genes from this assay revealed that when the plasmid expressing LEF-3 was deleted from the mixture, P143 remained in the cytoplasm. Plasmids were constructed where the synthesis of LEF-3 and P143 were directed by theie-1promoter. When these plasmids were cotransfected, both LEF-3 and P143 colocalized to the nucleus suggesting that an important function of LEF-3 is intracellular trafficking of P143 and directing it to the nucleus
Mucosal Transmission of Pathogenic CXCR4-Utilizing SHIVSF33AVariants in Rhesus Macaques

AbstractInfection of macaques with chimeric simian/human immunodeficiency virus (SHIV) expressing the envelope protein of HIV-1 provides a model system for studying HIV-1 infection in humans. To this end, four rhesus macaques (Macaca mulatta) were given a single intravaginal (IVAG) inoculation of cell-free SHIVSF33Aand longitudinal samples of peripheral blood and lymph nodes were analyzed for viremia, antigenemia, and various T-cell populations. Rhesus macaques infected IVAG with SHIVSF33Ademonstrated a dramatic decrease in the CD4+PBMC subset in the initial weeks after viral exposure, a time that corresponded to peak in plasma viremia and antigenemia. Within 4 months of SHIVSF33Ainoculation, partial to complete rebound of the CD4+PBMC was seen in these animals. Notably, the regeneration of the CD4+subset was associated with regeneration of the naive T-cell population and was concordant with clearance of plasma viremia. DNA heteroduplex tracking assays revealed transmission of minor variants within the SHIVSF33Ainoculum to the IVAG-inoculated animals. The cell-free SHIVSF33Ainoculum as well as virus isolated from animals early after transmission used the chemokine molecule CXCR4 as the primary cellular coreceptor, demonstrating that viruses expressing envelope glycoproteins of the syncytia inducing (SI) phenotype can be transported across the vaginal mucosa. Although none of the animals has yet to develop clinical symptoms of simian AIDS (SAIDS), infectious virus and viral nucleic acids could be persistently isolated from each animal. Furthermore, animals transfused with blood from IVAG-infected macaques drawn 2 weeks after inoculation suffered a more profound and sustained CD4+T-cell loss, persistent plasma viremia, and the development of SAIDS in one animal, indicating that IVAG-passaged SHIVSF33Awas pathogenic. Taken together, these results establish that a pathogenic CXCR4-utilizing SHIVSF33Aspecies crossed the cervicovaginal mucosa. Different courses of infection in the IVAG versus transfusion animals suggest that host-mediated responses elicited upon transmission across mucosal barriers may serve to limit viral replication and delay disease progression in the IVAG-infected animals
Morphopoietic Determinants of HIV-1 Gag Particles Assembled in Baculovirus-Infected Cells

AbstractThe determinants for HIV-1 particle morphology were investigated using various deletion and insertion mutants of the Gag precursor protein (Gag) expressed in baculovirus-infected cells and ultrastructural analysis of membrane-enveloped Gag particles under the electron microscope. Five discrete regions were found to influence the size, the variability in dimension, and the sphericity of the particles: (i) the matrix (MA) N-terminal domain, within residues 10–21, the junctions of (ii) MA–CA (capsid), (iii) CA-spacer peptide SP1 and (iv) nucleocapsid (NC)–SP2, and (v) the p6gagC-terminus. Internal regions (ii), (iii), and (iv) contained HIV-1 protease cleavage sites separating major structural domains. No particle assembly was observed foramb276, a MA–CA polyprotein mutant lacking the C-terminal third of the CA domain. However, MA–CA domains including the MHR (residues 277–306), or downstream sequence to CA residue 357, resulted in the assembly into tubular or filamentous structures, suggesting a helical symmetry of Gag packing. Mutantamb374, derived fromamb357 by further addition of the heptadecapeptide motif358HKARVLAEAMSQVTNSA374, overlapping the CA–SP1 junction and the SP1 domain, showed a drastic change in the pattern of Gag assembly, compared toamb357, with formation of spherical particles. These data suggested a novel function for the spacer domain SP1, acting as a spherical shape determinant of the Gag particle which would negatively affect the helical symmetry of assembly of the Gag precursor molecules conferred by the MHR and the downsteam CA sequence, within residues 307–357
AnArabidopsis thalianaMutant with Virus-Inducible Phenotype

AbstractThe role of host factors in plant viral diseases is not well understood. To study this important aspect of plant–pathogen interaction, we identified anArabidopsis thalianamutant, designatedvid1(virus-inducibledwarf), with altered responses to viral infection. Specifically,vid1resembled the wild-type plants when healthy but developed a severely dwarfed phenotype with a loss of apical dominance following infection by a tobamovirus. Genetic segregation showed that thevid1phenotype is caused by a recessive mutation in a single gene. Since systemic viral infection is thought to interfere with the host plant intercellular transport, we propose that thevid1mutation affects this transport process. Combination of the mutation and viral infection may disrupt transport of developmental regulators, such as hormones, causing formation of thevid1phenotype. Indeed, the effect ofvid1mutation was repressed by exogenous application of a plant hormone auxin. Potentially, thevid1mutant will help characterize the mechanism of virus–plant interaction and formation of plant viral disease symptoms
An Anti-HIV Peptide Construct Derived from the Cleavage Region of the Env Precursor Acts on Env Fusogenicity through the Presence of a Functional Cleavage Sequence

AbstractA 22-amino-acid-long multibranched peptide construct (CLV) derived from the cleavage region (KIEPLGVAPTKAKRR*VVQREKR*) of the human immunodeficiency virus (HIV) type-1 envelope precursor inhibits HIV infection (Virology,1996, 223, 406–408). We attempted to characterize its activity for Env expressedviaa recombinant vaccinia virus (rVV): gp160 cleavage was delayed, but not impaired, in the presence of CLV (10 μM), whereas neither Env production nor Env membrane expression was significantly altered. Through the synthesis of analogs, we concluded that the presence of a cleavage sequence was required for inhibition of syncytium formation by CLV in rVV-infected CD4+cell cultures: indeed, a single amino acid residue substitution (R*>S) in the cleavage sites presented by CLV abolished its activity. Other analogs allowed us to further determine the region of CLV which mediates its activity. The ability of a radiolabeled CLV analog to enter cells was also shown. Altogether, these data strongly suggest that CLV acts on Env fusogenicity at least partially through interference with gp160 processing
The Non-Permissive Infection of Insect (Gypsy Moth) LD-652 Cells by Vaccinia Virus

AbstractThe members ofPoxviridaefamily are among the most complex of animal viruses and subfamily members infect both vertebrate (Chordopoxvirinae) and invertebrate (Entomopoxvirinae) hosts, respectively. Vaccinia virus (VV) is the most commonly studied vertebrate virus and the entomopoxvirus ofAmsacta moorei(AmEPV) is the prototypic insect virus. AmEPV, while not able to productively infect vertebrate cells, does enter vertebrate cells and expresses early genes after which the infection aborts although the cells survive (Y. Li, R. L. Hall, and R. W. Moyer.J.Virol.71(12), 95579562, 1997). We show here that a recombinant VV, containing thelacZgene regulated by the cowpox virus A-type inclusion (ATI) late promoter, likewise does not productively infect insect cells. Our results suggest that the recombinant VV enters insect cells, host protein synthesis is inhibited, early gene expression is normal, and viral DNA replication occurs as does late protein synthesis. However, little if any proteolytic processing of late viral proteins, typical of morphogenesis, is observed. Electron micrographs of infected cells suggest that while cytoplasmic virosomes (factories) are formed, there is little indication of further morphogenesis or any formation of mature virions. Therefore, while both orthopoxviruses and entomopoxviruses fail to replicate in heterologous hosts, the nature of abortive infections is quite different
A Core Trimer of the Paramyxovirus Fusion Protein: Parallels to Influenza Virus Hemagglutinin and HIV-1 gp41

AbstractThe paramyxovirus fusion (F) protein mediates membrane fusion. The biologically active F protein consists of a membrane distal subunit, F2, and a membrane-anchored subunit, F1. We have identified a highly stable structure composed of peptides derived from the F1heptad repeat A, which abuts the hydrophobic fusion peptide (peptide N-1), and the F1heptad repeat B, located 270 residues downstream and adjacent to the transmembrane domain (peptides C-1 and C-2). In isolation, peptide N-1 is 47% α-helical and peptide C-1 and C-2 are unfolded. When mixed together, peptides N1 + C1 form a thermostable (Tm>90°C), 82% α-helical, discrete trimer of heterodimers (mass 31,300Mr) that is resistant to denaturation by 2% SDS at 40°C. We suggest that this α-helical trimeric complex represents the core most stable form of the F protein that either is fusion competent or forms after fusion has occurred. Peptide C-1 is a potent inhibitor of both the lipid mixing and the aqueous content mixing fusion activity of the SV5 F protein. In contrast, peptides N-1 and N-2 inhibit cytoplasmic content mixing but not lipid mixing, leading to a stable hemifusion state. Thus, these peptides define functionally different steps in the fusion process. The parallels among both the fusion processes and the protein structures of paramyxovirus F proteins, HIV gp41, and influenza virus hemagglutinin are discussed, as the analogies are indicative of a conserved paradigm for fusion promotion among fusion proteins from widely disparate viruses
Herpes Simplex Virus Type 1 Induction of Persistent NF-κB Nuclear Translocation Increases the Efficiency of Virus Replication

AbstractThe latent form of the dimeric transcription factor NF-κB is sequestered in the cytoplasm by proteins containing ankyrin repeats, such as IκBα and β, or by the p105 precursor form of the NF-κB p50 subunit. Tumor necrosis factor α or virus infection can cause targeted destruction of IκB and nuclear translocation of NF-κB. Following translocation, NF-κB mediates immune, inflammatory, or anti-apoptotic responses. Here we present evidence that beginning at around 6 h postinfection, herpes simplex virus (HSV) induces a persistent translocation of NF-κB into the nucleus of C33 cells, coincident with loss of both IκBα and IκBβ. Translocation failed to occur when infecting virus was preincubated with neutralizing antibody to viral envelope glycoproteins gD or gH, thus preventing entry, or when cells were infected with viruses expressing mutated forms of immediate-early regulatory proteins ICP4 or ICP27. Surprisingly, no increase in thetrans-activation function of NF-κB, as assayed by transient expression of CAT, was detected following HSV infection. The significance of NF-κB nuclear translocation for virus replication was demonstrated by an 80–90% reduction in virus yield following infection of C33 cells expressing a constitutive repressor form of IκBα. Models that reconcile nuclear translocation of NF-κB with the inability to detect NF-κB-dependent gene expression are discussed
The Human Immunodeficiency Virus Type 1 NEF Protein Binds the Src-Related Tyrosine Kinase Lck SH2 Domain Through a Novel Phosphotyrosine Independent Mechanism

AbstractPrimate lentiviruses encode for an uniquenefgene with an essential function in both viral replication and pathogenicity in the host. The molecular basis for this function remains however poorly defined. Several Nef-binding cellular proteins are thought to be instrumental in its function. Indeed, Nef contains a proline-rich motif implicated in the binding to the Src-like tyrosine kinase Hck and also to a Ser/Thr kinase of molecular weight 62 kDa. The disruption of this motif affects the binding to both these kinases as well as viral replication. Whereas Hck is expressed in the myeloid lineage and hence may account for theneffunction in infected monocytes, we and others have reported previously that Nef also interacts with the T-lymphocyte Src-kinase Lck, leading to specific cell signaling impairment. This interaction occurs through the binding of Nef to both Lck SH2 and SH3 domains. Both the proline motif and phosphorylation of Nef on tyrosine residue were proposed to account for these interactions. Here, we investigate the mechanism of Lck SH2 binding by HIV-1 Nef. Using recombinant fusion proteins to precipitate lysates, we show that although SH2 binding is dependent on phosphorylation events, it occurs in a tyrosine independent manner because it requires neither tyrosine residues in Nef nor the phosphotyrosine binding pocket from the Lck SH2 domain, hence suggesting a role for a phosphoserine or a phosphothreonine residue. Further, we show that Hck SH2 does not interact with Nef, indicating that Hck SH3 binding is sufficient for Nef binding, whereas Lck SH2 cooperates together with SH3 to allow Nef binding to a level similar to Hck SH3. Together, our results establish different mechanisms for Hck and Lck binding by HIV-1 Nef protein, and identify a novel mechanism for Src-like tyrosine kinase targeting by a viral protein
Repetitive DNA Insertion in a Protein Kinase ORF of a Latent FSV (Feldmanniasp. Virus) Genome

We describe the structure of aFeldmanniasp. virus (FsV) genome integrated in the brown alga,Feldmannia.This integrated FsV genome appears to be permanently inactivated and lost its ability to excise and replicate. Unlike the replicated form of FsV, this integrated FsV genome contains a large (>50 kb) repeat region inserted in a protein kinase open reading frame. While related to the 173-bp repeats previously characterized in the FsV genome (Leeet al., 1995), Southern blot analysis indicates that the repeats in the inactive, integrated FsV genome are distinct from those previously characterized. Fine structural analysis of the repeat-insertion sites in the protein kinase gene indicates that there are 8- and 10-bp palindromic sequences present in multiple locations located near the repeat-insertion site. The translated protein kinase contains all of the catalytic motifs conserved in most serine/threonine protein kinases and a potential autophosphorylation site. This protein kinase gene is expressed as RNA in sporophyte plants where virus production is active but not in gametophyte plants where the virus genome is latent. The structure of the integrated virus genome is discussed
Deletion of Proline-Rich Domain in Polyomavirus T Antigens Results in Virus Partially Defective in Transformation and Tumorigenesis

AbstractPolyomavirus productively infects mouse cells, transforms rat fibroblasts in culture, and induces a broad spectrum of tumors when inoculated into newborn mice. The expression of large, middle, and small T antigen are necessary for virus growth and oncogenic transformation. We have generated a small deletion in a region common to both large and middle T antigen that encodes three consecutive prolines. In this report we characterize this mutant virus in terms of its ability to replicate in mouse cells, transform rat fibroblasts, and induce tumors in the mouse. We find that the virus immortalizes primary cells and that viral DNA replication is not impaired, indicating that these functions of large T antigen are not altered. However, the ability of the virus to transform rat fibroblasts is defective. The mutant virus makes fewer foci and the foci are weaker in appearance. The mutant middle T still associates with PI 3-kinase and shc, suggesting that the overall structure of the protein has not been disrupted. When inoculated into newborn C3H mice, the mutant virus induces fewer overall tumors with a longer latency than wild-type virus. These results indicate that this proline-rich domain in middle T antigen is important for oncogenesis in a wide variety of tissues and cell types
Complementation of a Replication-Defective Mutant of Equine Herpesvirus Type 1 by a Cell Line Expressing the Immediate-Early Protein

AbstractEquine herpesvirus type 1 (EHV-1) possesses a sole, diploid immediate-early (IE) gene that encodes a major regulatory protein of 1487 amino acids capable of modulating expression of both early and late EHV-1 promoters and capable oftrans-repressing its own promoter. In this study, a rabbit kidney cell line (IE13.1) that constitutively expresses the EHV-1 IE protein was generated by cotransfection of rabbit kidney (RK-13) cells with the viral IE gene and a neomycin resistance marker. The IE protein expressed by this cell line was shown (1) to be expressed by and to localize to the nucleus of virtually all cells as demonstrated by indirect immunofluorescence, (2) to be the full-size IE polypeptide as judged by Western immunoblot analyses with an anti-IE protein-specific antibody, and (3) to be functional as shown by the transactivation of two representative EHV-1 early promoters linked to the chloramphenicol acetyltransferase reporter gene in transient transfection assays. The IE13.1 cell line was able to complement a recombinant virus in which both copies of the IE gene were replaced by insertion of theEscherichia coli lacZgene. This IE deletion mutant, designated KyAΔIE, was not able to replicate in equine, rabbit, or mouse cells but was capable of replication in the IE13.1 cells that provided the IE protein intrans. Rescue of the KyAΔIE virus was achieved by recombination with a marker plasmid that harbors the wild-type IE gene, and the rescued virus (KyAΔIER) was able to grow on noncomplementary cells. Overall, these results offer direct evidence that the IE gene is essential for EHV-1 replication and provide reagents useful for the analysis of IE protein function
A Single Nucleotide Substitution in the Transcription Start Signal of the M2 Gene of Respiratory Syncytial Virus Vaccine Candidatecpts248/404 Is the Major Determinant of the Temperature-Sensitive and Attenuation Phenotypes

AbstractRespiratory syncytial virus (RSV)cpts248/404 is a live-attenuated, temperature-sensitive (ts) vaccine candidate derived from cold-passagedcpRSV by two rounds of chemical mutagenesis and biological selection. Previous sequence analysis showed that these two steps introduced three single nucleotide substitutions into thecpRSV parent. Two of these occurred within the coding sequence for the L protein, and each resulted in a single amino acid substitution: Gln-831-Leu (248 mutation) and Asp-1183-Glu (404-L mutation). The third mutation resulted in a nucleotide substitution at position 9 of thecis-acting gene start signal of the M2 gene (404-M2 mutation). In the present study, the genetic basis of attenuation ofcpts248/404 was defined by the introduction of each of these mutations (singly or in combination) into a full-length cDNA clone ofcpRSV. Recombinant RSV derived from each mutant cDNA was analyzed to determine the contribution of each mutation to thetsand attenuation phenotypes of the virus. This analysis showed that the 248 mutation specifies a significant reduction of plaque formation at 38°C and is responsible for an intermediate level of attenuation in mice. In contrast, the 404-L mutation did not contribute to thetsor attenuation phenotype alone or in combination with other mutations and is thus an incidental change. Unexpectedly, the 404-M2 mutation alone specified complete restriction of plaque formation at 37°C and a high level of attenuation in mice. This indicates that the level of temperature sensitivity and attenuation ofcpts248/404 can be attributed primarily to the 404-M2 mutation. Thus thecpts248/404 virus contains a set oftsand non-tsattenuating mutations, which likely accounts for its genetic stability. The recombinant version of this virus, rA2cp248/404, was phenotypically indistinguishable fromcpts248/404 and represents a background into which additional mutations can be introduced as needed to obtain the desired level of attenuation for successful immunization of the very young human infant