Foot-and-Mouth Disease Virus-Induced Alterations of Baby Hamster Kidney Cell Macromolecular Biosynthesis: Inhibition of Ribonucleic Acid Methylation and Stimulation of Ribonucleic Acid Synthesis

The kinetics of ribonucleic acid (RNA) and protein synthesis and RNA methylation were examined after foot-and-mouth disease virus (FMDV) infection of baby hamster kidney cells. The synthesis of RNA extracted from the whole cells was stimulated two- to threefold above the control level of synthesis. This increased rate was attributed to viral RNA synthesis. The inhibition of host RNA methylation was concomitant with but more pronounced than protein synthesis inhibition. The methylation of transfer RNA was initially inhibited by virus infection, but rose to within 70 to 80% of the control level just prior to the production of maximal amounts of virus-specific RNA polymerase. Cycloheximide studies showed that rapid cessation of protein synthesis did not result in the immediate cessation of RNA methylation. A comparison between the kinetics of inhibition of these processes by cycloheximide and FMDV infection suggests that FMDV selectively inhibits RNA methylation.     

Ribosome Development and the Methylation of Ribosomal Ribonucleic Acid

Immature ribonucleoprotein particles accumulate in amino acid-starved cells of a relaxed mutant of Escherichia coli. The ribonucleic acid (RNA) of these particles is nonmethylated in cells starved for methionine. However, in bacteria starved for arginine, lysine, or histidine, the RNA of these particles is one-half methylated. The relationship of submethylation to a structural alteration in the same RNA was studied. The results of kinetic studies showed that submethylation and the structural transition are not causally related, since they are described by different rate constants. Moreover, it was possible to accumulate fully methylated immature-particle RNA that possessed the sedimentation and chromatographic properties of nonmethylated RNA. It was concluded that, during the normal course of ribosome development, methylation of ribosomal RNA is completed prior to the final maturation steps.     

Electrophoretic Characterization of Foot-and-Mouth Disease Virus-Specific Ribonucleic Acid

Foot-and-mouth disease virus (FMDV)-specific ribonucleic acid (RNA) was analyzed by electrophoresis on 0.5% agarose gels. Four classes of RNA were resolved as a function of mobility in agarose: two classes of slowly migrating multistranded RNA, the infectious viral RNA with intermediate mobility, and a minor fast-moving class of lower-molecular-weight single-stranded RNA. The major RNA species were infectious viral RNA and the slowest migrating class of multistranded RNA. The latter RNA was polydisperse when analyzed by sucrose gradient centrifugation, it was partially ribonuclease resistant, and it was the predominant RNA species labeled during the initial period of (3)H-uridine triphosphate incorporation in the cell-free system. Heat treatment studies indicated that part of the slowest-moving RNA was degraded at 60 C and almost complete degradation was detected at 100 C. It was concluded that this RNA is the replicative intermediate in viral RNA synthesis. The second class of multistranded RNA contained both a ribonuclease-resistant RNA and a second RNA peak which was detected only after heat treatment at temperatures above 75 C. Fractions of FMDV-specific RNA isolated by sucrose gradient centrifugation were analyzed by agarose-gel electrophoresis. Infectious viral RNA was detected only in the 37S zone and was the major species of RNA in this part of the gradient. The ribonuclease-resistant RNA (the 20S zone) contained about equal amounts of multistranded RNA (both classes) and the low-molecular-weight single-stranded RNA. All sucrose gradient fractions between 20 and 40S were found to contain the replicative intermediate, although the major portion was detected in the 20 to 25S region.     

Inhibition of Host-Cell Protein and Ribonucleic Acid Synthesis by Newcastle Disease Virus

The mechanisms of Newcastle disease virus-(NDV) induced inhibition of cell protein and ribonucleic acid (RNA) synthesis were investigated. It was observed that the ability of NDV to inhibit cell RNA synthesis is dependent on the virus strain. The inhibitors, azauridine and cycloheximide, were added to cell cultures at different times after infection to study the roles of protein and RNA synthesis in the viral inhibition process. Viral inhibition of cell RNA synthesis and viral inhibition of cell protein synthesis become resistant to cycloheximide at a different time after infection than that in which they become resistant to azauridine. The results indicate that the inhibition of cell RNA synthesis by the Texas strain involves the synthesis of inhibitory proteins which are coded by the viral genome. The Texas and Beaudette strains of NDV appear to employ different mechanisms for the inhibition of host-cell protein synthesis. Viral inhibition of cell protein synthesis does not appear to cause, or be the result of, viral inhibition of cell RNA synthesis.     

口蹄疫病毒诱导宿主细胞凋亡的研究

本文报道了口蹄疫病毒（Foot-and-Mouth Disease Virus,FMDV）在体外诱导PK－15细胞凋亡的研究结果,采用Hoechst33258荧光探针、DNA凝胶电泳、脱氧核糖核酸转移酶介导的制品末端标记（TUNEL）技术均检测到了典型的细胞凋亡,结果显示：使用感染性滴度为4.8lgTCID50/mL的口蹄疫病毒感染PK－15细胞,在培养32h后,荧光探针检测呈现典型的凋亡细胞核固缩和梅花状碎裂核,并伴随有凋亡小体出现,调亡率约为20％;DNA凝胶电泳显示ladder梯带;末端标记检测到强绿色荧光标记物结合于凋亡细胞核上。研究结果提示：口蹄疫病毒可以在体外诱导宿主细胞凋亡,细胞凋亡是其致细胞病变死亡的重要途径之一。     

口蹄疫病毒诱导宿主细胞凋亡的研究

本文报道了口蹄疫病毒（Foot-and-Mouth Disease Virus,FMDV）在体外诱导PK-15细胞凋亡的研究结果。采用Hoechst33258荧光探针、DNA凝胶电泳、脱氧核糖核酸转移酶介导的缺口末端标记（TUNEL）技术均检测到了典型的细胞凋亡。结果显示使用感染性滴度为4.8lgTCID50/mL的口蹄疫病毒感染PK-15细胞,在培养32?h后荧光探针检测呈现典型的凋亡细胞核固缩和梅花状碎裂核,并伴随有凋亡小体出现,凋亡率约为20%;DNA凝胶电泳显示ladder梯带;末端标记检测到强绿色荧光标记物结合于凋亡细胞核上。研究结果提示口蹄疫病毒可以在体外诱导宿主细胞凋亡,细胞凋亡是其致细胞病变死亡的重要途径之一。     

Inhibition of Ribonucleic Acid Bacteriophage Release from Its Host by Rifampin

Rifampin, in addition to interfering with intracellular growth of the ribonucleic acid-containing phage MS2, also inhibits the release of mature phage particles from Escherichia coli cells.     

Impairment of Host Cell Ribonucleic Acid Polymerase II After Infection with Frog Virus 3

Evidence is presented that, in frog virus 3-infected BHK cells, inhibition of ribonucleic acid (RNA) synthesis is paralleled by a decreased activity of host cell RNA polymerase II, while the template ability of host cell nuclei and chromatin is unaffected.     

Specific Inhibition of Mammalian Ribonucleic Acid C-Type Virus Deoxyribonucleic Acid Polymerases by Rat Antisera

Inhibition of the ribonucleic acid (RNA)- and deoxyribonucleic acid (DNA)-dependent DNA polymerase activities of mammalian C-type viruses was obtained with sera from rats bearing murine leukemia virus-induced transplant tumors. Polymerase activities of nonmammalian (viper) C-type virus and murine mammary tumor virus were not inhibited by such sera nor by serum from a rat immunized with the DNA polymerase of feline leukemia virus purified by isoelectric focusing. The latter serum appeared to inhibit preferentially the DNA-dependent DNA polymerase activity of mammalian C-type viruses showing no inhibition of RNA-dependent DNA synthesis.     

Inactivation of Foot-and-Mouth Disease Virus by Citric Acid and Sodium Carbonate with Deicers

Three out of five outbreaks of foot-and-mouth disease (FMD) since 2010 in the Republic of Korea have occurred in the winter. At the freezing temperatures, it was impossible to spray disinfectant on the surfaces of vehicles, roads, and farm premises because the disinfectant would be frozen shortly after discharge and the surfaces of the roads or machines would become slippery in cold weather. In this study, we added chemical deicers (ethylene glycol, propylene glycol, sodium chloride, calcium chloride, ethyl alcohol, and commercial windshield washer fluid) to keep disinfectants (0.2% citric acid and 4% sodium carbonate) from freezing, and we tested their virucidal efficacies under simulated cold temperatures in a tube. The 0.2% citric acid could reduce the virus titer 4 logs at −20°C with all the deicers. On the other hand, 4% sodium carbonate showed little virucidal activity at −20°C within 30 min, although it resisted being frozen with the function of the deicers. In conclusion, for the winter season, we may recommend the use of citric acid (>0.2%) diluted in 30% ethyl alcohol or 25% sodium chloride solvent, depending on its purpose.     

Inhibition of Influenza Virus Replication by Targeting Broad Host Cell Pathways

Antivirals that are currently used to treat influenza virus infections target components of the virus which can mutate rapidly. Consequently, there has been an increase in the number of resistant strains to one or many antivirals in recent years. Here we compared the antiviral effects of lysosomotropic alkalinizing agents (LAAs) and calcium modulators (CMs), which interfere with crucial events in the influenza virus replication cycle, against avian, swine, and human viruses of different subtypes in MDCK cells. We observed that treatment with LAAs, CMs, or a combination of both, significantly inhibited viral replication. Moreover, the drugs were effective even when they were administered 8 h after infection. Finally, analysis of the expression of viral acidic polymerase (PA) revealed that both drugs classes interfered with early events in the viral replication cycle. This study demonstrates that targeting broad host cellular pathways can be an efficient strategy to inhibit influenza replication. Furthermore, it provides an interesting avenue for drug development where resistance by the virus might be reduced since the virus is not targeted directly.     

Virus Interference by Cellular Double-Stranded Ribonucleic Acid

Ribonuclease-resistant ribonucleic acid (RNA) was isolated from uridine-labeled cultures of rabbit kidney, chicken embryo, and HeLa cells. This RNA, regardless of its source, was found to induce interference with virus growth in either rabbit kidney or chicken embryo cultures. Nuclease-treated cellular nucleic acids exhibited interference-inducing activity which eluted with a small fraction of RNA in the exclusion volume of a 6% agarose gel column. Besides resistance to ribonucleases, the interference inducer and RNA isolated from partially digested nucleic acids have in common two properties of double-stranded RNA: (i) similar sharp melting profiles were obtained for inducer and ribonuclease-resistant RNA, with T(m) dependent on NaCl concentration; (ii) ribonuclease-resistant inducer and RNA banded together in Cs(2)SO(4) density gradients at a density characteristic of known double-stranded RNA. After melting at low ionic strength, the labeled RNA shifted to a higher density and its capacity to inhibit virus replication was lost. Velocity sedimentation analysis of the cellular ribonuclease-resistant RNA indicated that the majority sedimented between 7 and 11S, but only RNA sedimenting at >==8 to 20S had a high specific activity of interference induction. Without prior ribonuclease treatment, the ribonuclease-resistant RNA can be precipitated with 2 m LiCl and thus appears to exist in purified cellular nucleic acids as part of molecular complexes with both single- and double-stranded regions of RNA. The biosynthesis of cellular double-stranded RNA is inhibited by actinomycin D.     

Thermally Induced Intracellular Alteration of Ribosomal Ribonucleic Acid

Heating at 55 C causes the intracellular degradation of ribosomes of Staphylococcus aureus MF-31. The 30S subunit of heated cells appears to be selectively attacked. Analysis of ribonucleic acid (RNA) showed that 16S RNA was destroyed and that the secondary structure of 23S RNA was altered.     

Small Ribosomal Ribonucleic Acid Species of Saccharomyces cerevisiae

Yeast ribosomes contain two small molecular-weight species of ribonucleic acid (RNA), in addition to transiently associated transfer RNA. The 5S RNA species is part of the large ribosomal subunit and appears to be exactly the same size as 5S RNA from other organisms. There is another RNA molecule, approximately 5.8S or 150 nucleotides in size, which is noncovalently attached to the 25S ribosomal RNA and can be freed by gentle heating or urea treatment. Neither 5 nor 5.8S RNA are methylated. The 5.8S RNA is probably derived from a part of the 35S precursor RNA, whereas the 5S RNA is made de novo. These results substantiate the notion that ribosome biosynthesis in yeast is analogous to that of the higher eukaryotes.     

Ribonucleic Acid Polymerase Induced by Vaccinia Virus: Lack of Inhibition by Rifampicin and α-Amanitin

The RNA polymerase activity present in the cytoplasm of BHK cells infected with vaccinia virus is not affected by rifampicin or by alpha-amanitin.     

Ribosomal Ribonucleic Acid Maturation During Bacterial Spore Germination

All the ribosomal ribonucleic acid made during the early stages of germination of spores of Bacillus subtilis is of the "precursor" type, i.e., that type appearing in the incomplete forms of the ribosome. Shortly before the onset of deoxyribonucleic acid synthesis in germination, this precursor ribonucleic acid changed to the mature ribosomal ribonucleic acid characteristic of the 30S and 50S ribosomal subunits.     

Relationship Between Sporulation-Specific 20S Ribonucleic Acid and Ribosomal Ribonucleic Acid Processing in Saccharomyces cerevisiae

The nature and properties of the 20S ribonucleic acid which accumulates only during the sporulation of Saccharomyces cerevisiae were examined. The 20S ribonucleic acid (RNA) has a base composition considerably different from ribosomal RNA species and is virtually unmethylated. The 20S RNA did, however, exhibit approximately 70% homology with 18S RNA by RNA-deoxyribonucleic acid filter hybridization competitions. The 20S RNA showed a hybridization saturation plateau level 30 to 40% higher than 18S, consistent with measurements of the size difference in polyacrylamide gels. Pulse-chase experiments in the presence and absence of cycloheximide indicate that the 20S RNA has a presumptive relationship to the 20S ribosomal RNA precursor normally observed only in short pulse-labeling in vegetative cells.     

Inhibition of Ribonucleic Acid Synthesis by Nalidixic Acid in Escherichia coli

The effect of low concentrations of nalidixic acid on ribonucleic acid (RNA) synthesis in Escherichia coli was examined. It was observed that RNA synthesis in exponentially growing cells was not significantly affected, in harmony with previous studies. However, RNA synthesis was markedly depressed by nalidixic acid during starvation for an amino acid or during chloramphenicol treatment. This effect was not caused by increased killing or inhibition of nucleoside triphosphate synthesis by nalidixic acid. The pattern of radioactive uracil incorporation into transfer RNA or ribosomes was not changed by the drug. The sensitivity of RNA synthesis to nalidixic acid in the absence of protein production may be useful in probing the amino acid control of RNA synthesis.