The Sequence of HIV-1 TAR RNA Helix Controls Cationic Distribution

Sequence dependency of metal ion aggregation around RNA structures is known to be involved in critical functions ranging from processes of molecular recognition to enzymatic chemistry. Ion interactions with an HIV-1 TAR RNA core helix were examined with explicit solvent molecular dynamics simulations. The results have shown that there is a sequence-dependent cationic localization toward the purine-rich run within the TAR helix and other purine-rich duplexes. The behavior is independent of ionic species or a presence of a bulge. A region of high ion affinity agrees very well with the position of the X-ray determined divalent cations within a fragment from the HIV-1 TAR RNA.