Importance of the positive-strand RNA secondary structure of a murine coronavirus defective interfering RNA internal replication signal in positive-strand RNA synthesis.

Repass, J F; Makino, S

The RNA elements that are required for replication of defective interfering (DI) RNA of the JHM strain of mouse hepatitis virus (MHV) consist of three discontinuous genomic regions: about 0.46 to 0.47 kb from both terminal sequences and an internal 58-nucleotide (nt)-long sequence (58-nt region) present at about 0.9 kb from the 5' end of the DI genome. The internal region is important for positive-strand DI RNA synthesis (Y. N. Kim and S. Makino, J. Virol. 69:4963-4971, 1995). We further characterized the 58-nt region in the present study and obtained the following results. (i) The positive-strand RNA structure in solution was comparable with that predicted by computer modeling. (ii) Positive-strand RNA secondary structure, but not negative-strand RNA structure, was important for the biological function of the region. (iii) The biological function had a sequence-specific requirement. We discuss possible mechanisms by which the internal cis-acting signal drives MHV positive-strand DI RNA synthesis.