Sequence of interrupted and uninterrupted mRNAs and cloned DNA coding for the two overlapping nonstructural proteins of influenza virus.

We have obtained the complete sequence of cloned full-length DNA (NS DNA) derived from influenza virus gene 8, which codes for two unique polypeptides, NS1 and NS2, and the sequence of the NS2 mRNA. Previously we showed that the mRNA for NS1 (approximately 860 nucleotides) is colinear with the viral RNA and maps from 0.05--0.95 units of the cloned NS DNA, and the body of the NS2 mRNA (approximately 340 nucleotides) maps from 0.59--0.95 units, suggesting that the two mRNAs are 3' co-terminal and share the same poly(A) addition site. Sequencing studies have shown that the NS2 mRNA contains an interrupted sequence of 473 nucleotides. The nucleotide sequences at the junctions of the interrupted segments are similar to those of the consensus sequences at the splicing sites of intervening regions in eucaryotic mRNAs. The first approximately 56 virus-specific nucleotides at the 5' end of the NS2 mRNA are the same nucleotides as are found at the 5' end of the NS1 mRNA, and this leader sequence of the NS2 mRNA contains the initiation codon for protein synthesis and coding information for nine amino acids which would be common to NS1 and NS2. In addition, both mRNAs contain 10--20 heterogeneous nonviral nucleotides at their 5' ends. The approximately 340 nucleotide body region of the NS2 mRNA can be translated in the +1 reading frame, and the sequence indicates that NS1 and NS2 overlap by 70 amino acids that are translated from different reading frames.