Interaction of poliovirus-encoded 2C/2BC polypeptides with the 3' terminus negative-strand cloverleaf requires an intact stem-loop b.

The poliovirus-encoded, membrane-associated polypeptide 2C and its precursor, 2BC, is believed to be required for initiation and elongation of viral RNA synthesis. Previous studies have shown that the 2C polypeptide specifically interacts with the 3'-terminal sequence of poliovirus negative-strand RNA. This interaction is facilitated by the presence of the conserved sequence UGUUUU in the "stem a" within the 3'-terminal cloverleaf structure. We show that the 2C precursor, 2BC, also interacts with the 3'-terminal cloverleaf of the negative-strand RNA. We also demonstrate here that interaction of 2C/2BC with the negative strand 3'-terminal sequence not only depends on an intact "stem a" containing the UGUUUU sequence but is equally influenced by the presence of an intact "stem b" within the negative-strand cloverleaf. The results presented here suggest that the spatial configuration of stem a UGUUUU sequence with respect to an intact stem-b is crucial for 2C/2BC interaction with the 3'-terminal negative-strand cloverleaf structure.