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The crystal structure of the hemagglutinin (HA) of influenza virus A/Aichi/68 (H3N2) from the X-31 reassortant virus was reported in 1981, but as yet there are no X-ray diffraction structures for hemagglutinins of other types or even subtypes of influenza virus. We have used site-directed mutagenesis to probe the structure of the hemagglutinin of influenza B/Hong Kong/8/73. We investigated a region...
Prior studies with recombinant viruses constructed in vitro showed that the V2 domain of envelope gp120, in addition to the required V3 domain, enhances the efficiency of infection of primary macrophages by HIV-1. Present structural studies on the gp120s of these recombinant viruses using three human monoclonal antibodies directed to the V3 loop indicate that the V2 domain affects cell tropism by...
Here we have investigated if human immunodeficiency virus type 1 (HIV-1) protease expressed in trans can interfere with production of infectious HIV-1 particles. Protease produced from a Tat and Rev inducible expression plasmid specifically cleaved HIV-1 p55Gag in a dose-dependent manner. Coexpression of protease and an infectious HIV-1 proviral clone resulted in increased intracellular cleavage of...
The matrix (M) protein of vesicular stomatitis virus (VSV) plays a central role in virus assembly by binding the nucleocapsid core to the viral envelope during the budding process. A small percentage of M protein molecules are phosphorylated in vivo, but the role of phosphorylation in M protein function is unknown. Using limited proteolysis, we previously determined the sites of in vivo phosphorylation...
In vitro-synthesized human T-cell leukemia virus type 1 (HTLV-I) Rex response element (Rex-RE) activates the interferon-induced 2', 5'-oligoadenylate synthetase (2-5OAS) in a dose-dependent manner. In addition, Rex-RE at 1 μg/ml activates a second interferon-induced enzyme, p68 kinase (PKR); however, at 50 μg/ml, Rex-RE inhibits PKR activity. Poly(rl)-poly(rC) (10 μg/ml) dissociates the ribonucleoprotein...
The in vitro RNA-binding activity of the movement protein (P1) of cauliflower mosaic virus was studied after its expression in Escherichia coli, purification, and uv-crosslinking to a radioactive probe. It was found that insoluble P1 aggregates were involved in RNA-binding activity. A series of deletion mutants were used to identify a domain within P1 required for binding activity. The RNA-binding...
A fatal case of hantavirus pulmonary syndrome (HPS) in northern California prompted our attempt to isolate viruses from local rodents. From tissues of two deer mice, Peromyscus maniculatus, two hantaviruses (Convict Creek virus 107 and 74, CC107 and CC74) were established in cell culture. Viral antigens, proteins, and RNAs of the first and archetypical isolate (CC107) were examined, and portions of...
A role for the large glycoprotein (G1) of California encephalitis (CE) virus was examined in the infection of baby hamster kidney (BHK-21) and Aedes albopictus (C6/36) cell lines and the mosquito Ae. dorsalis using G1 monoclonal antibodies (MAbs) and selective protein cleavage. Five MAbs neutralized CE viral infectivity in both cell lines. One MAb, 7D45, efficiently neutralized the peroral infection...
Most site-directed mutations in the gene encoding the small, membrane-associated 6K protein of Sindbis virus interfere selectively with virus assembly and budding. Particles are released that are aberrant in structure, with a single membrane enclosing multiple nucleocapsids. A revertant for the mutation that inserted a serine for a cysteine at position 39 in the 6K protein was isolated and found to...
Picornavirus RNAs interact with host cellular proteins to direct viral translation initiation by internal ribosome entry. In this study, we analyzed the RNA-protein interactions involving computer-predicted stem-loops F and G (also referred to as V and VI, respectively) of the 5' NCR of poliovirus RNA. This region of the 5' NCR harbors part of the putative internal ribosome entry site. We show that...
The gene encoding protein p17, a major structural protein of African swine fever virus, has been mapped and sequenced. Protein p17 was purified from dissociated virus by reverse-phase HPLC and the amino acid sequence of a peptide obtained after digestion of protein p17 with cyanogen bromide was determined by automated Edman degradation. To map the gene encoding protein p17, a mixture of 17-mer oligonucleotides...
The envelope glycoprotein complex is composed of two polypeptides, an external heavily glycosylated polypeptide (SU) and a membrane-spanning protein (TM). Together they form a heterodimer on the surface of the virion. These proteins are synthesized in the form of a polyprotein precursor which is glycosylated and proteolytically processed during its maturation in the secretory pathway. A highly conserved...
Varicella-zoster virus (VZV) encodes 69 unique open reading frames, 5 of which do not have herpes simplex virus type 1 (HSV-1) homologs. One of the 5, ORF1, is predicted to encode a protein of 108 amino acids. We identified a 470-base RNA corresponding to ORF1. To determine whether ORF1 encodes a protein, an 11-amino-acid epitope was inserted in frame after the ninth codon of the ORF1 open reading...
The tobacco etch potyvirus (TEV) capsid protein (CP) is necessary for cell-to-cell and long distance transport of the virus in plants. In this study, the transport phenotypes of TEV mutants containing CPs with a substitution of the highly conserved Ser122 (termed S122W) within the core domain, or with a deletion of sequences encoding 17 amino acid residues comprising most of the variable C-terminal...
The monopartite DNA genome of beet curly top geminivirus (BCTV, strain Logan) contains four leftward (complementary sense) open reading frames (ORFs) designated L1, L2, L3, and L4. We investigated the functions of the L2 and L3 ORFs by mutational analysis We found that in Nicotiana benthamiana and sugarbeet plants, neither a functional L2 nor a functional L3 gene is required for infectivity. Double...
Tax protein of HTLV-1 triggers transcriptional activation through enhancers, NF-κB binding site, 21-bp enhancer, and serum response element. Previously, we demonstrated binding of Tax to transcription factors NF-κBt p105 and p50. Here, we report that Tax enhances expression of HF-κB2 at the mRNA level and proteins; the effect was more apparent on the p52 expression than on its precursor p100, suggesting...
Previously, we obtained a neutralizing monoclonal antibody directed against the hemagglutinin-neuraminidase (HN) protein of human parainfluenza type 2 virus (PIV2), which was able to prevent cell fusion without affecting the hemagglutinating and neuraminidase activities. In this study, four escape mutants of PIV2 have been obtained under pressure of the monoclonal antibody. Intriguingly, the HN protein...
Two separate promoters, the upstream preS1 and the downstream S promoters, give rise to transcripts encoding three forms of the hepatitis B virus surface protein. Overproduction of large surface protein because of increased preS1 transcripts leads to a block in secretion of all forms of the surface protein and of virion particles. We show here that a CCAAT element in the S promoter not only increases...
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