PROTEIN AND RNA SYNTHESIS INHIBITION BY VESICULAR STOMATITIS VIRUS: AN ANALYSIS OF THE VIRAL COMPONENTS REQUIRED FOR INHIBITION (TRANSLATION, TRANSCRIPTION, INFECTION, TARGET-SIZE, LEADER)

Protein and RNA synthesis are inhibited when VSV infects certain cells. UV-inactivation analysis of the virus indicates that transcription of two regions of the viral genome are required for efficient inhibition. The larger of the two viral products represents transcription of approximately 1500 nucleotides and may represent the N protein gene, while the smaller product is approximately 40 nucleotides long. The latter product is thought to be encoded at the 3\u27-proximal end of the genome.^ Two viral mutants have been shown to be deficient in the expression of the smaller transcription product and result in less efficient inhibition of both protein and RNA synthesis. Analysis of these mutants and the UV-inactivated wild-type virus have allowed for the establishment of conditions where the effects of either the large or the small transcription product can be observed independent of the other. This will allow for the correlation of a viral product with inhibition, and thereby establish the causative agent(s) of inhibition. The striking similarities of the inhibition processes for protein and RNA synthesis suggests that protein synthesis inhibition may be a consequence of RNA synthesis inhibition. A likely candidate for the small transcription product is the plus-strand leader RNA, a 47-50 nucleotide long transcript encoded at the exact 3\u27-end of the viral genome. However, analysis of this viral product in wild-type and mutant virus-infected cells indicates that neither protein nor RNA synthesis inhibition correlate to the presence of the plus-strand leader RNA.^ In vitro translation in VSV-infected cell lysates have been shown to reflect the synthetic activity of the whole cell. When the lysates are treated with eukaryotic initiation factors (eIF-2 and eIF-4B/4F), there is a stimulation of synthesis in the VSV-infected cell lysates and this stimulation seems to require expression of the majority of the viral genome. The eIF-2 specific stimulation is quenched when cell extracts are pre-incubated with sera from patients having the Lupus auto-immune antibody to the La protein.