A structural model for the genome of echovirus 22.

We have proposed previously that the structural model for the echovirus 22 genome is a single-stranded RNA molecule that has folded back upon itself to form a stable "hairpin" at the 5'-terminus. The vRNA of echovirus 22 has been characterized further by digestion with selective ribonucleases, electrophoresis in composite gels, hydrodynamic studies in density gradients of Cs2SO4 and sucrose, thermal denaturation and 3'-terminal ribonucleotide analysis. Based on these observations, the genome of echovirus 22 is a single-stranded RNA molecule having a region of secondary structure located at the 5'-terminus that may be characterized as a snapback hairpin with hydrogen-bonded base-pairing. In addition, a VPg-like protein is attached (presumably to the 5'-end of the RNA) and the 3'-terminus contains a polyadenylic acid tract [poly (A)].