Isolation of poliovirus 2C mutants defective in viral RNA synthesis.

Two poliovirus mutants were isolated that contain an oligonucleotide linker insertion in the 2C-coding region of the viral genome. One, 2C-31, has a strongly temperature-sensitive phenotype and the other, 2C-32, forms small plaques on HeLa cell monolayers at all temperatures. Both mutants have a severe temperature-sensitive defect in viral RNA synthesis but little effect on the types of viral protein that are made. Temperature shift experiments showed that the 2C function is continuously required for viral RNA synthesis to proceed. The 2C mutants could be complemented in trans by mutants with mutations in other viral proteins. Protein 2C is also the locus of the guanidine resistance and dependence mutants, a drug whose action also affects viral RNA synthesis. Thus, protein 2C is one that is needed continually for viral RNA synthesis and, at least with these temperature-sensitive alleles, can be provided in trans.