The 3' untranslated regions of Kamiti River virus and Cell fusing agent virus originated by self-duplication.

Previously, it was shown that the 3' untranslated region (3'UTR) of Kamiti River virus (KRV) is nearly twice as long as the 3'UTR of other flaviviruses (1208 nucleotides compared with 730 nucleotides for the longest 3'UTR of any virus in the Tick-borne encephalitis virus species). Additionally, KRV and the closely related Cell fusing agent virus (CFAV) were shown to contain two short, almost perfect repeat sequences of 67 nucleotides. However, the construction of a robust comparative nucleotide alignment has now revealed that the double-length 3'UTR and the direct repeats resulted from the virtually complete duplication of a primordial KRV 3'UTR. We also propose that the CFAV 3'UTR was derived from a KRV-like precursor sequence with a large deletion that nevertheless preserved the two direct repeat sequences. These data provide new insights into the evolution of the flavivirus 3'UTR.