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.     

Inhibition of Host Cell Ribosomal Ribonucleic Acid Methylation by Foot-and-Mouth Disease Virus

A study of protein and ribonucleic acid (RNA) synthesis in cells infected by foot-and-mouth disease virus has indicated possible mechanisms of viral control over host cell metabolism. Foot-and-mouth disease virus infection of baby hamster kidney cells resulted in 50% inhibition of host cell protein synthesis at 180 min postinfection. A viral-induced interference with host cell RNA methylation was observed to be more rapidly inhibited than protein synthesis. To determine the nature of methylation inhibition, the kinetics of several host cell methylated RNA species were examined subsequent to virus infection. Data from sucrose zonal centrifugation and methylated albumin kieselguhr chromatography showed that methylation of nuclear RNA was inhibited 50% at 60 min postinfection. Inhibition of nuclear ribosomal RNA precursors and formation of nascent ribosomes correlated with inhibition kinetics of nuclear RNA methylation. It is suggested that the viral interference with the host nuclear RNA methylation is directly responsible for the observed loss of nascent ribosome formation. Moreover, early in the infectious cycle, methylation inhibition of host cell RNA could, in part, account for the cessation of host protein synthesis.     

Patterns of transcription in bacteriophage P22-infected Salmonella typhimurium.

Two peaks of RNA synthesis (early and late) are directed by bacteriophage P22 in lytic infections of Salmonella typhimurium. Late RNA synthesis is not seen in P22 23- infections; neither early nor late RNA synthesis occurs in P22 24- infections. Genes 23 and 24 of P22 appear to be analogous to genes Q and N of lambda, respectively.