The bipartite promoter of Orthonairovirus hazaraense large segment.

is a member of the genus of the that contains tri-segmented negative-strand RNA genomes with bipartite promoters for RNA synthesis. These promoters contain both virus-specific and segment-specific elements, the latter of which is apparently distinguished only by its ability to form a short double-stranded RNA (dsRNA) between the two ends of each genome segment as they emerge from the viral polymerase (the promoter duplex), to which the virus-specific elements are bound. Examination of the length and nucleotide composition of this duplex in a reporter minigenome system suggests that this promoter element acts via its separated single strands as well as dsRNA. IMPORTANCE The realization that segmented negative-strand RNA virus genome ribonucleoproteins are never free as their RNA ends are always bound to the viral polymerase has highlighted the problem of how these genome segments are replicated and express their mRNAs while their RNA ends remain associated with the polymerase throughout the cycles of RNA synthesis. This study of the length and nucleotide composition of the L segment-specific double-stranded RNA (dsRNA) promoter element (the promoter duplex) provides insight into how its mRNA might be initiated and suggests that this promoter element acts via its separated single strands as well as via dsRNA.