- Volume 72, Issue 12, 1991
Volume 72, Issue 12, 1991
- Animal
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A Transformation-specific Polypeptide Distinct from Heat Shock Proteins is Induced by Herpes Simplex Virus Type 2 Infection
More LessA tumour-specific polypeptide designated U90 is one of a set of polypeptides which are encoded by the host cell and are specific for the transformed cell state, being immunoprecipitated by the sera of tumour-bearing animals. The interest in these tumour-specific polypeptides centres on the finding that they are also recognized by antisera raised against herpes simplex virus type 2 (HSV-2)-infected cells, implying some role for HSV-2 in tumorigenesis. The peptide map of HSV-2-induced U90 is indistinguishable from that of U90 present in uninfected tumour cells, including mouse cells transformed by human papillomavirus type 16. In tumour cells, U90 is located principally in the plasma membrane fraction and cannot be induced by heat shock, glucose starvation, or treatment with tunicamycin or calcium ionophore. U90 is not related to either the heat shock protein of M r 90000 (HSP90) or the glucose-related polypeptide of M r 94000 (GRP94) as determined by peptide mapping and the use of monospecific, monoclonal and antipeptide antibodies. This suggests that U90 is a novel transformation-specific protein which can be induced by infection with HSV-2.
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Conversion of a Single-stranded Simian Virus 40 (SV40)-based Shuttle Vector to its Double-stranded Form does not Require the SV40 T antigen in Monkey Cells
More LessWe have transfected the single-stranded DNA form of the simian virus 40 (SV40)-based shuttle vector pZ189 into CV1P simian cells. Although the strand used did not code for the T antigen, we observed its conversion to a double-stranded DNA form. We deduced that the replication step converting a circular single-stranded DNA to a double-stranded one is independent of the SV40 T antigen in simian cells.
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Post-translational Processing and Oligomerization of the Fusion Glycoprotein of Human Respiratory Syncytial Virus
More LessThe post-translational maturation of the fusion protein (F) of human respiratory syncytial virus was investigated. Chemical cross-linking experiments indicated that F forms homotetramers and provided evidence that the intermonomer contacts involve primarily the F1 subunit. Homooligomerization as measured by sedimentation in sucrose gradients was insensitive to carbonyl cyanide m-chlorophenylhydrazone, indicating that it occurs in the endoplasmic reticulum. Cleavage of the F0 precursor to yield the F1 and F2 subunits was blocked by monensin or brefeldin A, indicating that it takes place in distal cisternae of the trans Golgi compartment or in the more distal trans Golgi network. The F0 precursor was not detected at the cell surface in surface immunoprecipitation experiments, indicating that cleavage is intracellular. The appearance of the cleaved F1 protein at the cell surface was concurrent with that of the attachment glycoprotein (G); this and other information indicated that the type 2 membrane orientation of G is not obligatorily associated with a reduced transit rate. Examination of F maturation in the presence of tunicamycin provided evidence that its expression at the cell surface depends upon cleavage and not directly upon glycosylation.
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Sequence Comparison Between the Haemagglutinin-neuraminidase Genes of Simian, Canine and Human Isolates of Simian Virus 5
More LessThe nucleotide sequence of the haemagglutinin-neuraminidase (HN) gene was determined for a simian (W3), human (LN) and two canine (CPI+/CPI-) isolates of simian virus 5 (SV5). A comparison of the predicted amino acid sequences revealed that the human and canine isolates varied from the simian isolate by 1.7% and 2.4% respectively. This lack of significant variation between the HN proteins of the four SV5 isolates suggests that insufficient differences have occurred between isolates to confine them to a specific host.
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- Plant
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Viruses in the Phytoreovirus Genus of the Reoviridae Family have the Same Conserved Terminal Sequences
More LessThe 5′- and 3′-terminal nucleotide sequences of the dsRNA genome segments of rice dwarf virus (RDV) and rice gall dwarf virus (RGDV), members of the Phytoreovirus genus of the Reoviridae family, were determined and compared with those of wound tumour virus (WTV). The 3′ tetranucleotides of the plus strand of all genome segments of RDV and RGDV were found to be the same (---UGAU 3′), except for segment 9 of RDV which had the 3′-terminal sequence ---CGAU 3′. The conserved 3′-terminal sequence (---UGAU 3′) was the same as that found in the genome segments of WTV, another member of the Phytoreovirus genus. On the other hand, the 5′ termini of the plus strands of RDV and RGDV were found to have two or three types of common sequence. RDV had either 5′ GGCAAA--- or 5′ GGUAAA---, whereas RGDV had 5′ GGCAUUUU---, 5′ GGUAUUUU--- or 5′ GGUAAUUU---. These conserved sequences were similar to the conserved 5′-terminal sequence of WTV (5′ GGUAUU---). Although the three viruses differ in plant host range, tissue specificity, vector specificity and disease symptom expression, these results suggest that they have a common ancestral origin.
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Biologically Active Transcripts of a Large Satellite RNA from Arabis Mosaic Nepovirus and the Importance of 5′ End Sequences for its Replication
More LessSynthetic transcripts of a satellite RNA associated with a lilac isolate of arabis mosaic nepovirus (ArMV) were made from cDNA clones. Transcripts having either six (M1R) or 29 (M3R) extra nucleotides at their 5′ ends replicated in the presence of ArMV genomic RNA in manually inoculated Chenopodium quinoa plants, even though M1R also differs from the native sequence at nucleotide position 2. Transcript 12R, which has 11 guanosyl residues and 27 other nucleotides not present in the natural satellite RNA at its 5′ end, and also lacks the two 5′-terminal nucleotides (UA), replicated inefficiently, both in transformed tobacco plants and in plants that had been manually inoculated. Transcripts from another construct (M2R) lacking eight 5′-terminal bases of the native sequence did not multiply in plants. Each of these transcripts directed the in vitro synthesis of a protein (M r 39K) encoded by satellite RNA, although 12R was the least efficient message. Analysis of the 5′-terminal sequences in progeny RNA from M1R showed that the non-native bases were removed and the second nucleotide corrected, suggesting that VPg plus a few initial 5′-terminal bases might serve as a primer for plus-strand synthesis of this satellite RNA. When M1R was inoculated with genomic RNAs from ArMV of ash or ivy, the transcripts replicated and were encapsidated. However, when the same amounts of M1R were inoculated with genomic RNAs of ArMV from hop or sugar-beet, progeny of the transcripts were not detected either in virions or in plants. Less surprisingly, this RNA transcript did not multiply in the presence of dogwood mosaic, strawberry latent ringspot, grapevine fanleaf or cherry leaf roll nepoviruses.
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Nucleotide Sequence of the Genomic RNA of Pepper Mild Mottle Virus, a Resistance-breaking Tobamovirus in Pepper
The entire genomic RNA of a Spanish isolate of pepper mild mottle virus (PMMV-S), a resistance-breaking virus in pepper, was cloned and sequenced and shown to be similar to other tobamoviruses in its genomic organization. It consisted of 6357 nucleotides (nt) and contained four open reading frames (ORFs) which encode a 126K protein and a readthrough 183K protein (nt 70 to 4908), a 28K protein (nt 4909 to 5682) and a 17.5K coat protein (nt 5685 to 6158). This is the first tobamovirus in which none of the ORFs overlap. Both its nucleic acid and predicted protein sequences were compared with the previously determined sequences of other tobamoviruses. The variations and similarities found and their relationship with the pathogenicity of this virus are discussed.
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Change in Phenotype and Encapsidated RNA Segments of an Isolate of Alfalfa Mosaic Virus: An Influence of Host Passage
More LessA local lesion isolate of alfalfa mosaic virus (AMV-N20) from lucerne was found to encapsidate two extra RNAs in addition to the four major RNAs (RNA1, -2, -3 and -4). These were resolved by gel electrophoresis both under native conditions and after glyoxal denaturation. The RNA with an electrophoretic mobility between that of RNAs 2 and 3 was designated RNA3l, that between RNAs 3 and 4 was designated RNA3s. Sucrose density gradient centrifugation analysis of AMV-N20 showed six instead of the normal four nucleoprotein components, the additional two presumably representing encapsidated RNAs 3l and 3s. RNAs 3l and 3s were both shown by Northern blot hybridization to be unrelated to host plant RNA and to contain the AMV coat protein gene sequence, which resides in RNA3. Primer extension of the RNAs 3l and 3s using a primer complementary to the 3′ common terminus of all genomic AMV RNAs provided further evidence that they contained AMV sequences. RNA31 represents an addition of about 255 nucleotides, compared with RNA3, and RNA3s represents a loss of about 308 nucleotides. The coat proteins of variants encapsidating either RNA3l, -3 or -3s had the same M r indicating that the addition or deletion of the nucleotides was outside the coat protein gene. Serial mechanical passage of AMV-N20 over 5 years in four host species led both to changes in the composition of the RNA3 mixture, and to changes in symptom severity. For example, following passage in Nicotiana clevelandii, RNA3 was lost whereas passage in either N. glutinosa, Chenopodium quinoa or C. amaranticolor resulted in the loss of RNA3l. No association was found between the changes in RNA3 and phenotypic changes that resulted from continuous passage for 5 years. Phenotypic changes with passage are thus presumably determined by mutations elsewhere in the virus genome.
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Diverse Groups of Plant RNA and DNA Viruses Share Related Movement Proteins that may Possess Chaperone-like Activity
More LessAmino acid sequences of plant virus proteins mediating cell-to-cell movement were compared to each other and to protein sequences in databases. Two families of movement proteins have been identified, the members of which show statistically significant sequence similarity. The first, larger family (I) encompasses the movement proteins of tobamo-, tobra-, caulimo- and comoviruses, apple chlorotic leaf spot virus (ACLSV) and geminiviruses with bipartite genomes. Thus this family includes viruses which move by two methods, those requiring the coat protein for the cell-to-cell spread (comoviruses) and those not having this requirement (tobamoviruses). The previously unsuspected relationship between the movement proteins of RNA and DNA viruses having no RNA stage in their life cycle (geminiviruses) suggested that their movement mechanisms might be similar. The second, smaller family (II) consists of the movement proteins of tricornaviruses (bromoviruses, cucumoviruses, alfalfa mosaic virus and tobacco streak virus) and dianthoviruses. Alignment of the sequences of family I movement proteins highlighted two motifs, centred at conserved Gly and Asp residues, respectively, which are assumed to be crucial for the movement protein function(s). Screening the amino acid sequence database revealed another conserved motif that is shared by a large subset of family I movement proteins (those of caulimo- and comoviruses, and ACLSV) and the family of cellular 90K heat shock proteins (HSP90). Based on the analogy to HSP90, it is speculated that many plant virus movement proteins may mediate virus transport in a chaperone-like manner.
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The Mechanism of Translation of Cowpea Mosaic Virus Middle Component RNA: No Evidence for Internal Initiation from Experiments in an Animal Cell Transient Expression System
More LessThe possibility that internal initiation of translation is responsible for the synthesis of the middle component (M) RNA-encoded 95K protein of cowpea mosaic virus (CPMV) has been investigated by constructing plasmids in which the entire sequence of CPMV M RNA was cloned downstream of a chloramphenicol acetyltransferase gene. Expression of these plasmids in an animal cell expression system revealed that no synthesis of the proteins encoded by the downstream CPMV open reading frame takes place from RNA derived from these constructs under conditions where the internal ribosome entry site of foot-and-mouth disease virus is functional. The results indicate that internal initiation is not responsible for the synthesis of the 95K protein in this system.
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Transmission of Cucumber Leaf Spot Virus by Olpidium Radicale
More LessThe ability of zoospores of four cultures of Olpidium radicale and one of O. brassicae to transmit viruses acquired in vitro from dilute virus solutions was compared. Transmission was demonstrated by infectivity and serological assays of the roots of cucumber seedlings 6 days after inoculation. A bulk culture of O. radicale, from cucumber plant roots collected near Nantes, France, a single-sporangial culture derived from it, and a single-sporangial culture from melon plant roots collected near Woodland, California, U.S.A., transmitted cucumber leaf spot virus (CLSV) and the cucumber fruit streak strain of CLSV (CLSV-FS). A bulk culture of O. radicale from melon plant roots collected at Montfavet, France, did not transmit CLSV or CLSV-FS. All four cultures transmitted cucumber necrosis and melon necrotic spot viruses, used as positive controls, but they did not transmit cucumber soil-borne, squash necrosis, petunia asteroid mosaic or tobacco necrosis viruses. In each of the trials a single-sporangial culture of O. brassicae from lettuce plant grown in California transmitted only tobacco necrosis virus.
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