Fine Mapping of a cis-Acting Sequence Element in Yellow Fever Virus RNA That Is Required for RNA Replication and Cyclization

We present fine mapping of a cis-acting nucleotide sequence found in the 5′ region of yellow fever virus genomic RNA that is required for RNA replication. There is evidence that this sequence interacts with a complementary sequence in the 3′ region of the genome to cyclize the RNA. Replicons were constructed that had various deletions in the 5′ region encoding the capsid protein and were tested for their ability to replicate. We found that a sequence of 18 nucleotides (residues 146 to 163 of the yellow fever virus genome, which encode amino acids 9 to 14 of the capsid protein) is essential for replication of the yellow fever virus replicon and that a slightly longer sequence of 21 nucleotides (residues 146 to 166, encoding amino acids 9 to 15) is required for full replication. This region is larger than the core sequence of 8 nucleotides conserved among all mosquito-borne flaviviruses and contains instead the entire sequence previously proposed to be involved in cyclization of yellow fever virus RNA.