Comparison of the structure and polypeptide composition of three double-stranded ribonucleic acid-containing viruses (diplornaviruses): cytoplasmic polyhedrosis virus, wound tumor virus, and reovirus

Isolation and genomic characterization of a cypovirus from Clanis bilineata

Clanis bilineata Walker, soybean hawkmoth, belongs to the subfamily Ambulicinae (Sphingidae, Lepidoptera) and is an edible insect that usually grows on soybean leaves. In this study, we isolated a new cypovirus from naturally diseased Clanis bilineata larvae (named CbCPV), scanned its structure, sequenced its genome, and studied its phylogenetic relationship to other cypoviruses. Microscopy showed that CbCPV polyhedral occlusion bodies were about 1.878 μm on average and contained many virions in the ultrathin sections. The complete genome sequence of CbCPV is 22,812 bp comprising 10 segmented double-stranded RNAs. Apart from segment 1 containing one open reading frame (ORF) and one sub-ORF, the other nine segments all contain one open reading frame and encoded one putative protein. The non-coding regions contained conserved sequences at 5' termini (AGUCAAA) and 3' termini (AGC), except segment 4 containing a different 5' termini (AUGUUUA). The whole sequence of the polyhedrin gene in CbCPV contained 892 nucleotides, encoding a protein of 246 amino acids. Based on amino acid sequences of polyhedrin or RNA dependent RNA polymerase (RdRp), the phylogenetic analysis indicated that CbCPV was closely related to DnCPV-23. The putative function of all segments differed from each other, but the most closely related species of segments were DnCPV-23 with 98.2-99.8% nucleotide identity. Overall, the evidence of morphology, protein analysis and nucleic acids (genomic pattern) showed that CbCPV is a new isolate in the cypovirus-23 type and can be termed Clanis bilineata cypovirus type 23 (CbCPV-23).

Molecular characterization of protein p50 of Dendrolimus punctatus cytoplasmic polyhedrosis virus

Genome segment 7 of the 10-segmented RNA genomes of Dendrolimus punctatus cytoplasmic polyhedrosis virus (DpCPV) comprises 1502 nucleotides with one ORF of 1347 bp. This ORF was predicted to encode a protein of 448 amino acids with a molecular mass of 49,756 Da (p50). Antisera against both p50 and an antigen domain (AD) near the N-terminus of p50 specifically bound to a viral structural protein of ca. 33 kDa (V5), indicating that V5 was an N-terminal product of p50. Immunoblotting analysis with anti-p50 antibodies detected p50 and V5 molecules in the host midguts three days and five days post infection, respectively. The intracellular localization of p50 protein was examined by expressing truncations of p50 fused with GFP in recombinant baculovirus-infected Sf9 cells. The p50 protein was present in the cytoplasm of the cells, and the N-terminal portion (67-135 aa) of the protein played a key role in this localization.

Expression of wound tumor virus gene products in vivo and in vitro

Infection of Agallia constricta vector cell monolayers with wound tumor virus results in the synthesis of 12 virus-specific polypeptides. Confirmation that these polypeptides are virus encoded rather than virus induced was obtained by cell-free translation of in vitro synthesized viral mRNA. In addition, transcription by purified wound tumor virus particles was coupled with translation of the resulting transcripts in a wheat embryo cell-free extract. Six previously described structural polypeptides, one presumptive structural polypeptide, and five previously unidentified nonstructural polypeptides were synthesized in infected vector cell monolayers, in cell-free extracts directed by in vitro synthesized viral mRNA, and in the homologous plant cell-free system, in which viral transcription was coupled with translation. Pulse-chase experiments revealed no evidence of precursor-product relationships for the wound tumor virus-specific polypeptides.

Molecular characterization of Bombyx mori cytoplasmic polyhedrosis virus genome segment 4

The complete nucleotide sequence of the genome segment 4 (S4) of Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) was determined. The 3,259-nucleotide sequence contains a single long open reading frame which spans nucleotides 14 to 3187 and which is predicted to encode a protein with a molecular mass of about 130 kDa. Western blot analysis showed that S4 encodes BmCPV protein VP3, which is one of the outer components of the BmCPV virion. Sequence analysis of the deduced amino acid sequence of BmCPV VP3 revealed possible sequence homology with proteins from rice ragged stunt virus (RRSV) S2, Nilaparvata lugens reovirus S4, and Fiji disease fijivirus S4. This may suggest that plant reoviruses originated from insect viruses and that RRSV emerged more recently than other plant reoviruses. A chimeric protein consisting of BmCPV VP3 and green fluorescent protein (GFP) was constructed and expressed with BmCPV polyhedrin using a baculovirus expression vector. The VP3-GFP chimera was incorporated into BmCPV polyhedra and released under alkaline conditions. The results indicate that specific interactions occur between BmCPV polyhedrin and VP3 which might facilitate BmCPV virion occlusion into the polyhedra.

Visualization of protein-RNA interactions in cytoplasmic polyhedrosis virus

Unlike the multiple-shelled organization of other Reoviridae members, cytoplasmic polyhedrosis virus (CPV) has a single-shelled capsid. The three-dimensional structures of full and empty CPV by electron cryomicroscopy show identical outer shells but differ inside. The outer surface reveals a T=1 icosahedral shell decorated with spikes at its icosahedral vertices. The internal space of the empty CPV is unoccupied except for 12 mushroom-shaped densities attributed to the transcriptional enzyme complexes. The ordered double-stranded RNA inside the full capsid forms spherical shells spaced 25 A apart. The RNA-protein interactions suggest a mechanism for RNA transcription and release.

Protein Synthesis in a Lymantria dispar Cell Line Infected by Cytoplasmic Polyhedrosis Virus

The efficiency of replication of a cytoplasmic polyhedrosis virus isolated from a member of the order Lepidoptera, Euxoa scandens, was studied in eight different lepidopterean cell lines. Lymantria dispar cells, which were found to support viral replication, more efficiently, were used to follow the kinetics of appearance of viral-specific polypeptides by a 2-h pulse with [ 35 S]methionine. Five polypeptides (ca. 120,000 molecular weight [120K], 105K, 66K, 46K, and 28K) were identified as components of the polyhedral inclusion bodies, and two polypeptides (112K and 39K) were assigned as viral-particle polypeptides. All these polypeptides were present after 24 h and were still being produced 96 h after infection. The rate of synthesis of the major polyhedral polypeptide (28K) increased in the time course of infection, whereas the background of cellular polypeptides seemed to be unaffected. An indirect immunoperoxidase technique, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis was blotted to a nitrocellulose membrane, showed that traces of the major polyhedral polypeptide were found from 8 h postinfection.

Polyadenylylation of proteins in reovirions

The reovirus oligoadenylates exist in two states within the virion: free and bound to viral proteins. The latter class of oligonucleotides, after digestion with Penicillium (P1) nuclease, yields adenylic acid and an adenosine-containing compound that is positively charged at pH 1.7, 3.5, or 6.5. In a mixture of [35S]methionine- and [3H]adenosine-labeled reovirus disrupted by sodium dodecyl sulfate/urea, approximately 4% of the radioactivity in [35S]methionine-labeled proteins coelutes with [3H]adenosine-labeled material at a net charge of -1.5 when analyzed by ion-exchange chromatography on DEAE-cellulose. This material migrates in sodium dodecyl sulfate/polyacrylamide gels with mu polypeptides and with a small protein, viii. Radioactivity is not released when the complex is boiled in buffer containing sodium dodecyl sulfate and urea or boiled in 80% dimethyl sulfoxide or when viral RNA is extracted with phenol. Digestion with Pronase converts the [3H]adenosine-labeled compound to oligomers of net charge -8 to -12 which contain nuclease P1- and alkaline phosphatase-sensitive adenylic acid residues as well as adenosine in a P1- and phosphatase-resistant linkage. These data indicate that reovirus contains structural proteins that are covalently bound to an oligoadenylate moiety.

"Methylation-coupled" transcription by virus-associated transcriptase of cytoplasmic polyhedrosis virus containing double-stranded RNA

S-adenosyl-L-methionine (SAM) activated the virus-associated RNA polymerase of cytoplasmic polyhedrosis virus in vitro. Synthesis of single-stranded viral RNA (mRNA) proceeded depending on the presence of SAM.A methyl residue of SAM was incorporated into an RNA molecule. A ribose moiety of adenylic acid in the 5'-terminal region of the nascent RNA was methylated in the very early stage of the transcription. The dependence of the viral transcription on the presence of SAM and the methylation of terminal nucleotide suggests that the transcription of CPV is a "methylation-coupled" reaction.

Analysis of a viral agent isolated from multiple sclerosis brain tissue: characterization as a parainfluenzavirus type 1

A virus originally isolated from cell cultures obtained by lysolecithin-induced fusion of human multiple sclerosis brain cells with CV-1 cells has been analyzed for its antigenic, RNA, and polypeptide compositions, and for selective biological properties. Our findings establish that this isolate, designated 6/94 virus, contains a 50S RNA genome and is, as yet, indistinguishable from Sendai virus in its antigenic and total polypeptide compositions. Despite these similarities, the 6/94 and Sendai viruses differ in certain phenotypic properties. 6/94 virus is markedly less cytocidal for chick fibroblasts, especially at 37 C and, after beta-propiolactone inactivation, it possesses a greater capacity for cell fusion and a lower toxicity than does comparably treated Sendai virus. In addition, 6/94 virus shows greater hemolytic activity.

Studies on the topography of reovirus and bluetongue virus capsid proteins

Protein labeling experiments confirm the surface location of proteins 2 and 5 in bluetongue virus, and proteins sigma3 and mu2 in reovirus. Lambda 2 is the major surface component of the reovirus core, and proteins 1, 3, and 4 appear to be the outer components of the bluetongue virus subviral particle.