Effect of protein binding on the twist-stretch coupling of double-stranded RNA

The elasticities of RNAs are generally essential for their biological functions, and RNAs often become functional when interacting with their binding proteins. However, the effects of binding proteins on the elasticities of double-stranded (ds) RNAs, such as twist-stretch coupling, still remain little understood. Here, our extensive all-atom molecular dynamics simulations show that the twist-stretch coupling of dsRNAs can be reversed from positive to negative by their binding proteins. Our analyses revealed that such a reversing effect of binding proteins is attributed to the protein anchoring across the major groove of dsRNAs, which alters the dominating deformation pathway from a major-groove-mediated one to a helical-radius-mediated one through two base-pair parameters of slide and inclination. Meanwhile, the anchoring effect from binding proteins on dsRNAs is further ascribed to the strong electrostatic attractions between dsRNAs and the positively charged binding domain of the proteins.