Isolation and preliminary characterization of temperature-sensitive mutants of encephalomyocarditis virus

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Abstract
Thirty temperature-sensitive mutants of encephalomyocarditis virus were isolated and partially characterized. Fifteen of these mutants are phenotypically RNA+, 13 are RNA- and 2 are RNA.+-.. Six RNA+ mutants, 1 RNA- mutant and 1 RNA.+-. mutant have virions which are more thermosensitive at 56.degree. C than the wild-type virions. HeLa [human cervical carcinoma] cells infected at the nonpermissive temperature with any of the RNA+ mutants produced neither infective nor noninfective viral particles. The cleavage of the precursor polypeptides in cells infected with 11 of the RNA+ mutants was defective at the nonpermissive temperature. This defect in cleavage occurred only in those precursor polypeptides leading to capsid proteins.