The S RNA segment of Sandfly Fever Sicilian virus: evidence for an ambisense genome

The complete nucleotide sequence of the S RNA segment of Sandfly Fever Sicilian (SFS) virus (Phlebovirus, Bunyaviridae) was determined from overlapping cDNA clones and by primer extension. The RNA is 1746 nucleotides in length and has two large open reading frames (ORF), one of which (24.8 kDa) is viral-complementary in sense, and the other (30.4 kDa) is in the viral sense. This ambisense genome arrangement has been seen in another member of the Phlebovirus genus, Punta Toro (PT) virus (T. Ihara, H. Akashi, and D. H. L. Bishop, 1984, Virology 136, 293-306), but not in representatives of either the Bunyavirus or Hantavirus genera of the Bunyaviridae. Comparison of the predicted amino acid sequences for SFS virus with the recognized products of PT S RNA (T. Ihara, Y. Matsuura, and D. H. L. Bishop, 1985, Virology 147, 317-325; H. A. Overton, T. Ihara, and D. H. L. Bishop, 1987, Virology 157, 338-350) indicated that the 24.8-kDa ORF encodes the nucleoprotein (N) of SFS virus, and the 30.4-kDa ORF codes for a nonstructural protein (NSs). Subgenomic messenger RNAs, from which these two proteins are presumably translated, were detected in virus-infected cells.