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At least 721 records · Page 40Linked to original sources
PubMed1994

Processing of E1 and E2 glycoproteins of hepatitis C virus expressed in mammalian and insect cells.

Processing of the envelope glycoproteins (E1 and E2) of hepatitis C virus (HCV) was investigated by using cDNA clones covering the structural and part of the nonstructural (NS) protein regions. The cDNA clones expressed in mammalian and insect cells were immunoprecipitated by serum of a hepatitis C patient and by monoclonal and polyclonal antibodies raised against the recombinant proteins expressed in insect cells or Escherichia coli. The E2 protein expressed in both insect and mammalian cells was a glycoprotein of 60 kDa (gp60) and removal of the sugar residues by N-glycanase yielded 38- and 40-kDa proteins. Pulse-chase experiments revealed that efficient expression and processing of the envelope proteins required coexpression with the flanking core and NS2 proteins. Not only E1 and E2 proteins but also NS2 and NS3 proteins were coprecipitated by anti-E1 or anti-E2 monoclonal antibody in the cells infected with the recombinant baculovirus expressing structural and NS proteins (NS2 and NS3), while only the NS3 protein was precipitated by anti-NS3 antibody. The association of E1 and E2 proteins was not influenced by the presence of a reducing agent and was still observed in the cells coinfected with the deletion mutants lacking both internal and C-terminal hydrophobic regions of each protein. Furthermore, the truncated forms of the E1 and E2 proteins were secreted into the culture supernatant and some of them were still associated with each other.

Animals↗
PubMed1996

Identification of baculovirus gene that promotes Autographa californica nuclear polyhedrosis virus replication in a nonpermissive insect cell line.

A gene that promotes Autographa californica M nuclear polyhedrosis virus (AcMNPV) replication in IPLB-Ld652Y cells, a cell line that is nonpermissive for AcMNPV, was identified in Lymantria dispar M nuclear polyhedrosis virus (LdMNPV). Cotransfection of AcMNPV DNA and a plasmid carrying the LdMNPV gene into IPLB-Ld652Y cells results in AcMNPV replication. The gene maps between 43.3 and 43.8 map units on the 162-kbp genome of LdMNPV. It comprises a 218-codon open reading frame and encodes a polypeptide with a predicted molecular mass of 25.7 kDa. The predicted polypeptide is glutamic acid and valine rich and negatively charged, with a pI of 4.61. No protein sequence motifs were identified, and no matches with known nucleotide or peptide sequences were found in the AcMNPV genome or database searches that suggest how this gene might function. A recombinant AcMNPV bearing the LdMNPV gene overcomes a block in protein synthesis observed in AcMNPV-infected IPLB-Ld652Y cells. Using Southern blotting techniques, we were unable to identify a homolog in Orgyia pseudotsugata M nuclear polyhedrosis virus, a baculovirus that is routinely propagated in IPLB-Ld652Y cells. This suggests that the LdMNPV host range is unique among the baculoviruses studied to date. We named this gene hrf-1 (for host range factor 1).

Amino Acid Sequence↗
PubMed1995

An RNA-dependent RNA polymerase activity associated with virions of tomato spotted wilt virus, a plant- and insect-infecting bunyavirus.

An RNA-dependent RNA polymerase activity was found associated with virions of tomato spotted wilt virus (TSWV), a plant- and insect-infecting member of the family Bunyaviridae. Radiolabeled nucleoside triphosphates were incorporated into trichloroacetic acid-precipitable products by detergent-disrupted, purified TSWV virions. Incorporation was reduced to near-background levels when RNase was present in the reaction mixture. The predominantly double-stranded RNA products were RNase-resistant at high but not low salt concentrations. The activity required manganese and was independent of a DNA template. Discrete products of approximately 3.0 kb and heterogeneous smaller products were synthesized that hybridized to purified TSWV RNA and transcripts of cDNA clones encompassing parts of each of the three genomic RNAs. The predominant products were viral sense although significant amounts of viral complementary sense S RNA products were also synthesized.

Datura stramonium↗
PubMed1993

Measles virus nucleocapsid protein expressed in insect cells assembles into nucleocapsid-like structures.

The gene encoding the major nucleocapsid, N, protein of measles virus has been inserted into a baculovirus vector under the control of the polyhedrin promoter. Insect cells infected with this recombinant baculovirus synthesize high levels of measles N protein, up to 40% of total soluble cell protein. The recombinant protein is recognized by sera from convalescent patients, vaccinees and patients with subacute sclerosing panencephalitis and thus could form the basis of a simple diagnostic assay. Nucleocapsid-like structures, similar to those found in mammalian cells infected with measles virus, can be observed in both the nucleus and cytoplasm of the infected insect cells. These have many structural features in common with nucleocapsids found in measles virus-infected cells, but are longer (up to 2 microns) and have a lower buoyant density. Measles N protein thus appears to be capable of assembling into nucleocapsid-like structures in the absence of measles virion RNA or other viral proteins.

Animals↗
PubMed1976

A small RNA virus with a divided genome from Heteronychus arator (F.) [Coleoperai Scarabaeidae].

Some properties of a small RNA virus isolated from larvae of Heteronychus arator [Coleoptera: Scarabaeidae] are described. The virus develops in the cytoplasm of gut and fat body cells and is 30 nm in diamter. The sedimentation coefficient of virus was 137S and the buoyant density was 1-33 g/ml. The single stranded RNA was isolated as two species which sedimented at 22S and 15S, corresponding to mol. wt. of 1-0 and 0-5 X 10(6) respectively. The base ratios of the two RNA species were 22 S: A=29-0, C=24-1, G¿-8, U=24-1; 15S:A=26-4, C=23-8, G=24-7, U=25-2. There was one major polypeptide, mol. wt. 40 000 and two minor polypeptides in the virus. The virus was infective for Galleria mellonella and some other insects, but was not infective for mice. No evidence was obtained to suggest that the two RNA species were present in different particles.

Animals↗
PubMed1990

Molecular cloning, characterization, and expression of the Tipula iridescent virus capsid gene.

The capsid protein is the major structural component of the icosahedral Tipula iridescent virus (TIV) that replicates in cytoplasmic inclusion bodies of insect cells. TIV capsid protein purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was digested with trypsin and fractionated by reverse-phase high-pressure liquid chromatography. A mixed oligonucleotide constructed from the amino acid sequence of a capsid tryptic peptide was used for the identification and cloning of the corresponding gene. The single-copy capsid gene, located on a 2.47-kilobase-pair HindIII TIV genomic fragment, codes for a 464-amino-acid protein (50,831 daltons) with a predicted pI of 6.34. Analysis of total RNA from infected Estigmene acrea cells indicated that the 1.8-kilobase capsid transcript was maximally produced between 14 and 24 h after infection. Transcript mapping by primer extension indicated that the RNA start site was in the A+T-rich TGCTACTAAT sequence, 19 nucleotides upstream from the first ATG codon of the capsid open reading frame. Expression of the TIV capsid protein in infected E. acrea cells was demonstrated by in vivo labeling of total proteins with [35S]methionine, using anti-capsid antiserum as the probe. Capsid protein was also expressed in Escherichia coli cells by using a pUC19 plasmid containing a lacZ-capsid gene fusion.

Amino Acid Sequence↗
PubMed1995

Expression of tobacco ringspot virus capsid protein and satellite RNA in insect cells and three-dimensional structure of tobacco ringspot virus-like particles.

The capsid protein gene of tobacco ringspot virus (TobRV), which had been modified to contain an amino-terminal methionine codon, was ligated into a baculovirus transfer vector downstream from the polyhedrin promoter. The resulting plasmid was cotransfected with linearized baculovirus DNA into insect cells. Recombinant baculovirus expressed high levels of the TobRV capsid protein that assembled to form virus-like particles that were similar in size and shape to authentic TobRV capsids. These virus-like particles did not encapsidate any RNA, including the capsid protein mRNA. The capsid protein mRNA is a truncated RNA 2, which may lack a putative encapsidation signal. To determine whether an intact packaging substrate could be encapsidated by the TobRV capsid protein, another recombinant baculovirus, concomitantly expressing both capsid protein and TobRV satellite RNA, was constructed. Surprisingly, the vast majority of the satellite RNA molecules expressed from this recombinant baculovirus were ligated in the insect cells to form circular RNA molecules. Like circular forms of satellite RNA generated in planta, these circular satellite molecules remained unencapsidated by the TobRV capsid protein. Computer-generated three-dimensional reconstruction using electron cryomicrographs of the empty virus-like particles allowed the first structural analyses of any nepovirus capsid. This 22-A resolution reconstruction resembled capsids of other members of the picornavirus superfamily. These data support the hypothesis that the nepovirus capsid is structurally analogous to those of the como- and picornaviruses.

Animals↗