pinecone/core-2020-05-10-deduplication huggingface dataset:
Entry of Rotaviruses Is a Multistep Process

AbstractThe infection of epithelial cells by some animal rotavirus strains requires the presence of sialic acid (SA) on the cell surface. Recently, we isolated rhesus rotavirus variants, named nar, whose infectivity, like that of human rotaviruses, is not dependent on SA. In this work, we have determined the binding properties of these SA-dependent and -independent rotavirus strains to MA104 cells. The half-time of attachment of the SA-dependent porcine rotavirus YM and reassortant virus DS1xRRV was found to be about 10 times longer in neuraminidase-treated cells than in untreated cells. On the other hand, human rotaviruses Wa and DS1, and the variant nar3, bound to cells two to three times more rapidly in the absence of SA. To investigate whether the SA-independent cellular structure recognized by the variant and human rotaviruses was the same, we used an infection assay designed to detect competition for cell surface molecules at both attachment and postattachment steps. In this assay, human rotavirus Wa efficiently competed the infectivity of YM in untreated cells and that of the variant nar3 in untreated, as well as neuraminidase-treated, cells. This competition was nonreciprocal, since YM and nar3 did not compete, but rather increased three- to fivefold the infectivity of Wa. In contrast, a two-direction competition between the variant nar3 and DS1xRRV was found. Similar results were obtained when psoralen-inactivated viruses were used as competitors, indicating that the competition observed was during the early stages of infection. Altogether, these results suggest the existence of multiple interactions between rotaviruses and the cell surface and revealed the existence of common steps during the entry of human and animal rotavirus strains
HPV 16 E6 Blocks TNF-Mediated Apoptosis in Mouse Fibroblast LM Cells

AbstractThe interaction between hosts and the viruses that infect them is a dynamic one, and a growing literature documents the fact that many viruses have developed mechanisms designed to avoid elimination by the host immune system. One of the immune strategies used by the host and targeted by virus proteins is apoptosis triggered by the cytokine tumor necrosis factor (TNF). Mouse fibroblast LM cells are spontaneously sensitive to TNF. When the wild-type E6 protein from the human papillomavirus type 16 (HPV 16) was expressed in LM cells, the cells became resistant to TNF. This resistance was examined by several means, including cell morphology, the dose- and time-independent response to TNF in a cell death ELISA, trypan blue exclusion, and cell proliferation. The level of p53 did not rise in TNF-treated cells prior to apoptosis, suggesting a p53-independent mechanism. Significant, though not complete, resistance to TNF was also observed following transfection of a plasmid expressing a mutant E6 protein, which is unable to mediate rapid degradation of the p53 tumor suppressor. These results indicate that the HPV 16 E6 protein can protect LM cells from TNF-triggered apoptosis and likely does so by a mechanism other than mediation of p53 degradation
The Rift Valley Fever Virus Nonstructural Protein NSs Is Phosphorylated at Serine Residues Located in Casein Kinase II Consensus Motifs in the Carboxy-Terminus

AbstractThe S segment of Rift Valley fever virus (Bunyaviridae, Phlebovirus) codes for two proteins, the nucleoprotein N and the nonstructural protein NSs. The NSs protein is a phosphoprotein of unknown function that is localized in the cytoplasm and the nuclei of infected cells where it forms filamentous structures. To characterize further the protein expressed in VC10 cells infected with the MP12 strain, we analyzed its phosphorylation states and showed that phosphorylated forms were found in both compartments. Cytoplasmic and nuclear NSs were phosphorylated only at serine residues. Phosphopeptide mapping and molecular analysis of mutants obtained by site-directed mutagenesis allowed us to map the major phosphorylation sites of nuclear and cytoplasmic forms of NSs to serine residues 252 and 256, located at the carboxy-terminus in consensus sequences for casein kinase II. A similar map was obtained when the protein was purified from mosquito cells infected with MP12. In addition, we showed that the purified unphosphorylated NSs protein expressed from pET-NSs plasmid in a coupled transcription–translation reaction containing Escherichia coli S30 extracts did not possess autophosphorylation activity but was phosphorylated in vitro after incubation with recombinant casein kinase II
Activation of p53 Tumor Suppressor by Hepatitis C Virus Core Protein

AbstractIn addition to being a structural protein that packages the viral genomic RNA, hepatitis C virus (HCV) core protein possesses regulatory functions. In this report, we demonstrate that the HCV core protein could enhance the gene transactivation activity of the tumor suppressor p53, regardless of whether p53 was derived from an exogenous or an endogenous gene. The activation of p53 by the HCV core protein was supported by the observation that the HCV core protein could enhance the expression of p21waf1/Cip1, a downstream effector gene of p53, in a p53-dependent manner. Further studies indicated that the HCV core protein could also suppress hepatocellular growth via p53. The HCV core protein and p53 could bind to each other in vitro, which was evidenced by the coimmunoprecipitation, the GST pull-down, and the Far-Western blot assays. The deletion-mapping analysis indicated that the carboxy-terminal sequence of p53 located between amino acids 366 and 380 was required for the core protein binding. These results raised the possibility that the HCV core protein might activate p53 through direct physical interaction. The persistent perturbation of p53 activity by the HCV core protein during chronic infection may have important consequences in HCV pathogenesis
The A20 Protein Interacts with the Epstein–Barr Virus Latent Membrane Protein 1 (LMP1) and Alters the LMP1/TRAF1/TRADD Complex

AbstractThe Epstein–Barr virus (EBV) latent membrane protein 1 (LMP1) interacts with the tumor necrosis factor receptor (TNFR)-associated factor (TRAF) molecules, which are important for LMP1-mediated signaling. Two domains of LMP1 can independently activate NF-kB, carboxyl-terminal activating region 1 (CTAR1) and CTAR2. The activation of NF-kB by CTAR1 occurs through direct interaction of LMP1 with the TRAF molecules, whereas CTAR2 interacts with the TNFR-associated death domain protein (TRADD) to activate NF-kB and the c-Jun N-terminal kinase (JNK). A20, which is induced by LMP1 through NF-kB, can block NF-kB activation from both domains of LMP1 and inhibit JNK activation from CTAR2. A20 also has been shown to associate with TRAF1 and TRAF2. In this study, an interaction between LMP1 and A20 was detected that was increased by TRAF2 overexpression. A20 did not affect the association of TRAF1 with TRAF2 but did displace TRAF1 from the LMP1 complex. The interaction of LMP1 and TRADD was decreased in the presence of A20, and the LMP1-A20 association was decreased by TRADD, suggesting that A20 and TRADD both interact with LMP1 and may compete for binding. These data indicate that A20 alters the interactions between LMP1 and the TRAF molecules and TRADD, affecting the activation of NF-kB, JNK, and perhaps other TRAF-mediated signaling events
Pyrimidine-Rich Region Mutations Compensate for a Stem-Loop V Lesion in the 5′ Noncoding Region of Poliovirus Genomic RNA

AbstractFive revertants of a linker-scanning mutation adjacent to the stem-loop V attenuation determinant (X472) in the 5′ noncoding region of poliovirus RNA were independently isolated from neuroblastoma cells and contained RNAs with seven nucleotide changes in the pyrimidine-rich region. Generation of the identical rare second-site mutations suggests the existence of a replicase-dependent mutagenesis mechanism during poliovirus replication. Enzymatic structure probing of the mutated pyrimidine-rich domain identified secondary structure changes between stem-loops V and VI. A consensus secondary structure model is presented for wild-type stem-loops V and VI and the pyrimidine-rich region located in the 5′ noncoding region of poliovirus RNA. A pyrimidine-rich region mutant (X472-R4N) produced large plaques in neuroblastoma cells and small plaques in HeLa cells, but the plaque size differences were not due to cell-type differences in viral translation or RNA replication. Release of X472-R4N from HeLa cells was 10-fold lower than release from neuroblastoma cells, which may explain the small plaque phenotype of X472-R4N in HeLa cells. Wild-type poliovirus was also released more efficiently from neuroblastoma cells (∼4-fold increase compared with release from HeLa cells), indicating that poliovirus neurotropism may be influenced by the cell-type efficiency of virus release. Thermal treatment increased the levels of infectious X472-R4N virions but not wild-type virus particles; thus RNA sequence and structural changes in the mutated 5′ noncoding region of X472-R4N may have altered RNA–protein interactions necessary for virus infectivity
The Open Reading Frame 3 of Equine Arteritis Virus Encodes an Immunogenic Glycosylated, Integral Membrane Protein

AbstractOpen reading frame 3 (ORF 3) of equine arteritis virus (EAV) is predicted to encode a glycosylated membrane protein (GP3) that is uncharacterized. ORF 3 of the American Type Culture Collection strain of EAV was in vitro transcribed and the encoded GP3 protein was in vitro translated with and without canine microsomal membranes. The GP3 protein was approximately 17 kDa after in vitro translation without canine microsomal membranes whereas the glycosylated form, after translation with microsomal membranes, was a diffuse band of 36–42 kDa, indicating that the GP3 protein is extensively glycosylated. Deglycosylation reduced the GP3 protein to approximately 17 kDa, the same size as that translated without microsomal membranes, indicating that the signal sequence was not cleaved. The EAV GP3 protein was membrane associated and not released as a soluble protein, in marked contrast to the ORF 3-encoded proteins of some other arteriviruses. The GP3 protein was protected from protease digestion in closed membrane vesicles, suggesting that the protein extends into the membrane vesicles and is anchored by the N-terminal signal sequence, a C-terminal hydrophobic domain, or both, but does not span the membrane three times. A GP3 protein lacking the C-terminal transmembrane domain remained membrane associated, indicating that this terminus is not a necessary membrane anchor. Sera from stallions persistently infected with EAV and horses immunized repeatedly with the modified live EAV vaccine contained antibodies specific for the GP3 protein. The data indicate that the GP3 protein is an extensively glycosylated membrane protein that is immunogenic during some EAV infections
Impaired Antiviral Response in Human Hepatoma Cells

AbstractHepatitis B, C, and D viruses can infect liver cells and in some individuals establish a chronic phase of infection. Presently, relatively little information is available on the antiviral mechanisms in liver cells. Because no good in vitro model infection systems for hepatitis viruses are available, we have used influenza A, Sendai, and vesicular stomatitis (VSV) viruses to characterize interferon (IFN) responses and IFN-induced antiviral mechanisms in human hepatoma cell lines. HepG2 or HuH7 cells did not show any detectable IFN-α/β production in response to influenza A or Sendai virus infections. Treatment of cells with IFN-α resulted in upregulation of IFN-α-inducible Mx, 2′,5′-oligoadenylate synthetase (OAS) and HLA class I gene expression but only with exceptionally high levels of IFN-α (≥100 IU/ml). Accordingly, high pretreatment levels of IFN-α, 1000 IU/ml for influenza A and VSV and 100 IU/ml for Sendai virus, were required before any detectable antiviral activity against these viruses was seen. IFN-γ had some antiviral effect against influenza A virus but appeared to be ineffective against VSV and Sendai virus. IFN-γ upregulated HLA class I protein expression, whereas Mx or OAS expression levels were not increased. There was a modest upregulation of HLA class I expression during Sendai virus infection, whereas influenza A virus infection resulted, after an initial weak upregulation, in a clear decrease in HLA class I expression at late times of infection. The results suggest that hepatoma cells may have intrinsically poor ability to produce and respond to type I IFNs, which may contribute to their inability to efficiently resist viral infections
The Virion Host Shutoff Function of Herpes Simplex Virus Degrades the 5′ End of a Target mRNA before the 3′ End

AbstractDuring lytic infections, the virion host shutoff (vhs) function of herpes simplex virus (HSV) disaggregates host polysomes and induces rapid turnover of both cellular and viral mRNAs. To examine the steps in vhs-induced mRNA degradation, an RNase protection assay was used to compare the relative decay rates of sequences from the 5′ and 3′ ends of a selected target mRNA. In cells infected with wild-type HSV-1, sequences at the 5′ end of the HSV-1 thymidine kinase mRNA were degraded more rapidly than those at the 3′ end of the transcript. In contrast, in cells infected with a vhs mutant, the decay rates of sequences at the 5′ and 3′ termini of the transcript were much slower and were essentially indistinguishable from each other. Vhs-induced degradation of the transcribed portion of the mRNA was not preceded by detectable shortening of the poly(A) tail in vivo; nor was a poly(A) tail required to make an RNA a target for the vhs activity in vitro. The results suggest that degradation of sequences at or near the 5′ end of an mRNA is an early step in vhs-induced decay
Mutations of Respiratory Syncytial Virus Attachment Glycoprotein G Associated with Resistance to Neutralization by Primate Polyclonal Antibodies

AbstractThe respiratory syncytial (RS) virus attachment glycoprotein G is a type II transmembrane glycoprotein and an important target of the host immune response. Antigenic variability of the G protein is postulated to contribute to the ability of the virus to evade established immune responses. A glycoprotein G monospecific polyclonal antiserum from a nonhuman primate was used to select for an antibody resistant RS virus. The mutant virus was resistant to neutralization by the selecting antiserum and by the sera from three other G-protein immunized primates. G-protein amino acid changes were found at residues 61 (Phe to Leu), 174 (Ser to Cys), and 183 (Trp to Leu). Thus the mutant protein had amino acid changes in the transmembrane domain (61) and the central ectodomain (174 and 183). The change at amino acid 174 resulted in five rather than the usual four Cys found in the conserved central region of the ectodomain. These data demonstrate that an RS virus with resistance to neutralization by polyclonal antibodies can be selected readily in cell culture. In addition, only a limited number of amino acid changes is required to produce the resistant phenotype
Altered Replication of Human Immunodeficiency Virus Type 1 (HIV-1) in T Cell Lines Retrovirally Transduced to Express Herpesvirus saimiri Proteins StpC and/or Tip

AbstractHuman peripheral blood T lymphocytes are transformed in vitro to continuous proliferation by Herpesvirus saimiri subgroup C strains. It has been previously shown that H. saimiri-transformed human T cell lines are a permissive system for HIV-1 and 2 replication and are highly susceptible to infection by HIV-1 and 2. Two open reading frames of H. saimiri, StpC and Tip, are required for T cell transformation and are unique to this herpesvirus. The successful transduction of human T cells with retroviral vectors expressing H. saimiri proteins StpC and Tip has allowed us to extend the previously mentioned observations and investigate the role of StpC and Tip in replication of HIV-1 T-tropic strains (IIIB, MN, and RF) in human T cell lines. StpC expression in Molt4 dramatically enhanced HIV-1 replication as measured by Tat protein expression, syncytia formation, and accumulation of reverse transcriptase activity. In contrast, Tip expression in Molt4 cells inhibited HIV-1 replication and cytopathic effects relative to Molt4 cells transduced with the empty vector alone. The StpC-induced phenotype dominated in Molt4 cells transduced to express both StpC and Tip, suggesting that StpC is responsible for facilitating HIV-1 replication in H. saimiri-transformed T cells. Colony-forming ability of Tip-expressing Molt4 cells following HIV-1 infection was greatly enhanced over Molt4 cells expressing either StpC or no H. saimiri proteins at all. HIV-1 proviral DNA could be detected by PCR in surviving Molt4 cells expressing StpC or Tip, indicating that a persistent infection was established. A better understanding of the effects of Tip and StpC proteins on the biology of human hemopoietic stem cells may lead to novel therapeutic interventions for the treatment of AIDS
Open Reading Frame in Rotavirus mRNA Specifically Promotes Synthesis of Double-Stranded RNA: Template Size Also Affects Replication Efficiency

AbstractThe 11 rotavirus mRNAs are capped, but not polyadenylated, have a high AU content, and serve as templates for the synthesis of double-stranded (ds)RNA. Earlier studies using a cell-free replication system showed that the 5′- and 3′-untranslated regions (UTRs) of the mRNAs have cis-acting signals that promote minus-strand synthesis. To identify additional factors that affect RNA replication, chimeric RNAs were made that consisted of portions of the gene 8 mRNA of SA11 rotavirus and of the gene for green fluorescent protein (gfp) or for the N protein of respiratory syncytial virus. Analysis of the chimeras in the cell-free replication system under noncompetitive conditions showed that the open reading frame (ORF) of viral mRNAs contains information that specifically promotes minus-strand synthesis. Results were also obtained indicating that a high AU content may increase the replication efficiency of RNAs and that, in general, an inverse correlation exists between replication efficiency and the length of the RNA template. Replication assays performed under competitive conditions showed that nonviral RNAs can interfere significantly with the replication of viral mRNAs, mostly likely by sequestering nonspecific RNA-binding proteins that are of limited concentration in the replication system and that are essential for dsRNA synthesis. In summary, rotavirus dsRNA synthesis is affected by many factors including cis-acting replication signals located in the 5′-UTR, 3′-UTR, and ORF of the mRNA as well as the size and possibly the AU content of the mRNA
Mammalian Reovirus M3 Gene Sequences and Conservation of Coiled-Coil Motifs near the Carboxyl Terminus of the μNS Protein

AbstractNucleotide sequences of the mammalian orthoreovirus (reovirus) type 1 Lang and type 2 Jones M3 gene segments were newly determined. The nucleotide sequence of the reovirus type 3 Dearing M3 segment also was determined to compare with a previously reported M3 sequence for that isolate. Comparisons showed Lang and Dearing M3 to be more closely related than either was to Jones M3, consistent with previous findings for other reovirus gene segments. The μNS protein sequences deduced from each M3 segment were shown to be related in a similar pattern as the respective nucleotide sequences and to contain several regions of greater or less than average variability among the three isolates. Identification of conserved methionine codons near the 5′ ends of the Lang, Jones, and Dearing M3 plus strands lent support to the hypothesis that μNSC, a smaller protein also encoded by M3, arises by translation initiation from a downstream methionine codon within the same open reading frame as μNS. Other analyses of the deduced protein sequences indicated that regions within the carboxyl-terminal third of μNS and μNSC from each isolate have a propensity to form α-helical coiled coils, most likely coiled-coil dimers. The new sequences will augment further studies on μNS and μNSC structure and function
Implication of the C-Terminal Domain of Nef Protein in the Reversion to Pathogenicity of Attenuated SIVmacBK28-41 in Macaques

AbstractWe have analyzed the nef gene sequences amplified from 12 macaques presenting various patterns of infection with SIVmacBK28-41, a clone derived from attenuated SIVmacBK28. We have observed seven mutation hot spots at positions 56, 75, 432, 588, 680, 699, and 779. The major alteration was a thymidine insertion at position 699, leading to a frameshift in the SIVmacBK28-41 nef gene and changing the last 15 amino acids of Nef into a 31-amino-acid-long C-terminal domain nearly identical to that encoded by pathogenic SIVmac239 and SIVmac251. The insertion was found at early time points in proviruses obtained from rapid progressor macaques, after 2 years postinfection in progressors, and rarely or only after 4 years postinfection in nonprogressors. Fixation of the other mutations occurred only after insertion of thymidine 699. Phylogenetic analysis demonstrated that the nef genes isolated from progressors evolved from the allele present in SIVmacBK28-41 to alleles present in SIVmac239 or SIVmac251, whereas nef sequences from nonprogressors stayed clustered with that of the inoculated molecular clone. These data stress the importance of the C-terminal extremity of the Nef protein of SIVmac239 or SIVmac251 in viral pathogenesis
A Genetically Engineered Cell Line Resistant to Subgroup J Avian Leukosis Virus Infection (C/J)

AbstractA cell line (DF-1\J) expressing the envelope protein isolated from the ADOL-Hc1 strain of the avian leukosis virus subgroup J (ALV-J) was used to analyze receptor interference to six different isolates of ALV-J as well as ALV subgroups A–D. The traditional gag-specific enzyme-linked immunosorbent assay (ELISA) as well as flow cytometry was used to evaluate viral infection. The parental cell line (DF-1) was susceptible to all ALV subgroups tested while the DF-1\J cell line was selectively resistant to the subgroup J isolates. The DF-1\J cell line was resistant to infection by all six ALV-J isolates as determined using the gag-specific ELISA. There was no interference with the other ALV subgroups (A–D) induced by the expression of the ADOL-Hcl envelope. The ALV-J isolates used in this analysis are serologically distinct when analyzed by flow cytometry. Convalescent sera to ADOL-Hcl cross-reacts with all of the ALV-J isolates tested; however, sera to HPRS-103 did not bind to four of the six isolates. Based on the intensity and differential binding of these antisera using flow cytometry, the six ALV-J isolates used can be grouped into four categories. Thus the DF-1\J cell line is resistant to infection by a serologically and genetically diverse group of ALV-J isolates and should be useful as a diagnostic tool
Mutation Analysis of cis-Elements in the 3′- and 5′-Untranslated Regions of Satellite Tobacco Necrosis Virus Strain C RNA

AbstractThe putative, 3′-terminal stem-loop structure in satellite tobacco necrosis virus strain C (STNV-C) RNA constitutes an essential cis-acting structure for the promotion of negative-strand RNA synthesis and a single-stranded tail is also important. The putative, 5′-terminal stem-loop structure in STNV-C RNA is not essential for productive, plus-strand RNA accumulation but is required for optimal accumulation. Residues 2 and 3 are the minimal cis-acting sequences required for RNA synthesis. The RNA of chimeric mutants, which exchanged 3′- and 5′-untranslated regions between STNV-C and helper tobacco necrosis virus strain D RNAs, accumulated in protoplasts, implying similar replication mechanisms for both RNAs