Dependence of RNA Replication on Continuous Protein Synthesis in a Temperature-sensitive Mutant of Foot-and-Mouth Disease Virus

A temperature-sensitive mutant of foot-and-mouth disease virus (FMDV) of the RNA^- phenotype induces active RNA dependent RNA polymerase only at the permissive temperature. Once induced this enzyme is active when assayed under cell-free conditions, even at the non-permissive temperature. However, when the enzyme is induced at the permissive temperature and the cultures are shifted to the non-permissive temperature, a sharp decline in activity is observed. The RNA^- character can be phenocopied by blocking protein synthesis. The evidence obtained suggests that virus RNA replication is dependent on continuous production of the enzyme.