The influenza C virus NS gene: evidence for a spliced mRNA and a second NS gene product (NS2 protein).

It has previously been shown that the shortest RNA (RNA 7) of influenza C viruses codes for a nonstructural (NSI) protein (Nakada et al. (1985) J. Virol. 56, 221-226). Experiments reported here indicate that RNA 7 also directs the synthesis of a second nonstructural protein via a spliced mRNA. The amino terminal 62 codons of this NS2 protein appear to be shared with the NS1 protein and the carboxyl terminal 59 amino acids are unique (derived from a +1 open reading frame in the mRNA). Although the size of the C virus NS2 protein is comparable to that of the A and B virus NS2 proteins, the overall arrangement of the C virus NS gene is quite different from that of the A and B virus NS genes. The second (+1) open reading frame of the C virus NS gene is completely overlapped by that of the NS1 protein, whereas the second (+1) open reading frame of the A and B virus NS genes extends to the 3' end of the RNA and only partially (or in some strains not at all) overlaps the NS1 open reading frame.