Composition of the sequence downstream of the dengue virus 5' cyclization sequence (dCS) affects viral RNA replication.

RNA replication of dengue virus (DENV) requires an RNA–RNA mediated circularization of the viral genome, which includes at least three sets of complementary RNA sequences on both ends of the genome. The 5′ and the 3′ untranslated regions form several additional RNA elements that are involved in regulation of translation and required for RNA replication. Communication between the genomic termini results in a structural reorganization of the RNA elements, forming a functional RNA panhandle structure. Here we report that the sequence composition downstream of the 5′ CS element in the capsid gene, designated as downstream CS (dCS) sequence – but not the capsid protein – also influences the ability of the viral genome to circularize and hence replicate by modulating the topology of the 5′ end. These results provide insights for the design of reporter sub-genomic and genomic mosquito-borne flavivirus constructs and contribute to the understanding of viral RNA replication.