Figure 1.

HIV-1_NL4-3 5′-leader and Ψ^CES RNA construct. (A) Predicted secondary structure of the HIV-1 5′-leader (16); gray shading denotes elements detected in the intact leader by NMR (13, 15); dark letters denote Ψ^CES (non-native residues colored red; see text). (B and C) Substitution of the native DIS loop residues (DIS-native) by GAGA (DIS-GAGA) prevents dimerization (B) but does not affect NC binding (C). (D) Representative NOESY spectra for G⁸A-Ψ^CES (black) and G-Ψ^CES (green); lines connect H8 (vertical labels) and H₁′ (horizontal labels) signals. (E) Representative very long-range NOE (A268-H₂ to C252-H₁′; ~ 7 Å separation) obtained for A^2rC^r-Ψ^CES.