Large RNA segment of Dugbe nairovirus encodes the putative RNA polymerase

The nucleotide sequence of the large (L) RNA segment of Dugbe (DUG) virus (Nairovirus, Bunyaviridae) was determined, completing the first entire genome sequence of a nairovirus. The L segment comprised 12255 nucleotides, making a total genome size of 18855 nucleotides, and the ends showed identity with the ends of the medium (M) and small (S) genomic segments. A single open reading frame (ORF) was present in the viral complementary strand, sufficient to encode a protein of 459 kDa. The predicted protein sequence showed the core polymerase motifs characteristic of the RNA-dependent RNA polymerases of segmented negative-stranded viruses. Comparison of the conserved motifs with the corresponding region of other segmented negative-strand viruses showed a closer relationship between nairoviruses and phleboviruses than with other Bunyaviridae or with other virus families. However, the core polymerase was the only function that could be assigned to a region of the DUG L gene.