Coding strategy of the S genome segment of Hantaan virus

Hantaan virus is the type species of the recently recognized Hantavirus genus of Bunyaviridae. The small (S) RNA segment of the negative-sense, tripartite genome was molecularly cloned and the nucleotide sequence was determined. The RNA sequence derived from the cDNA copy was found to contain 1696 nucleotides. A single open reading frame of sufficient size to encode the virus nucleocapsid protein was detected in the cDNA corresponding to viral complementary-sense RNA. RNA transcripts of the cDNA were synthesized with SP6 polymerase and were used to program cell-free reticulocyte lysate translation systems. Viral complementary-sense transcripts served as efficient messages in translation systems and generated Hantaan nucleocapsid protein. No translation products were detected when lysates were programmed with viral-sense transcripts. This coding assignment of the nucleocapsid protein to the viral complementary-sense RNA of the S genome segment is consistent with those of other members of this family. Unlike other Bunyaviridae, which encode both a nucleocapsid protein and a nonstructural (NSs) protein of similar sizes, a NSs protein has not been identified for Hantaan virus. Furthermore, other than the nucleocapsid protein gene sequence, the only potential open reading frame in Hantaan S RNA encoded a short, 48-amino acid polypeptide which initiated two codons beyond the termination of the nucleocapsid protein in the same reading frame. These data demonstrate that the coding strategy of the Hantaan virus S RNA is different than those reported for other viruses in this family.