Complete nucleotide sequence of Colorado tick fever virus segments M6, S1 and S2.

The nucleotide sequences of the tenth (M6), eleventh (S1) and twelfth (S2) dsRNA genomic segments of the Florio strain (N-7180) of Colorado tick fever virus were determined and found to be 675, 998 and 1884 bp, respectively, in length. A nonanucleotide motif and a hexanucleotide motif were found to be highly conserved in the 5' and 3' non-coding regions (NCRs), respectively, of the three segments. The first and last three nucleotides of each segment were of inverted complementarity, and segment-specific inverted terminal repeats were detected in the NCRs of the three segments. These findings suggest the occurrence of intracellular panhandle structures for the RNA transcripts. A readthrough phenomenon is suspected in segment M6. The environment surrounding the opal codon (position 1052-1054) of segment M6 conforms to that of leaky opal codons described in the literature.