Fig. 1. Mimicking directional unfolding of ZIKV xrRNA1 in the α-HL nanopore.

a, b Secondary (a) and tertiary structure (b) of ZIKV xrRNA1, which contains several tertiary interactions (cyan: U4·A23:U41 base triple, green: A36:U50 reverse pair) and two pseudoknots, PK1 (red, U2G3:C43G44) and PK2 (orange, G30-G33:C53-C56). In addition, one Mg²⁺ is found to coordinate with the phosphate of C5, A6, and C22 (pink). c A cartoon shows that xrRNA1 can resist the degradation by exoribonuclease Xrn1 from 5′→3′ direction, yet be traversed by the viral RdRP from 3′→5′ direction. d Cartoons showing the directional unfolding and translocation of ZIKV xrRNA1 through the α-HL nanopore, where a 36 nt poly(rA) leader sequence was co-transcribed with xrRNA1 at the 5′- or 3′-end to facilitate its translocation through the nanopore.