Assignment and NOE analysis of 2'-hydroxyl protons in RNA: implications for stabilization of RNA A-form duplexes

The ribose 2'-OH hydroxyl group distinguishes RNA from DNA. The 2'-OH hydroxyl protons are responsible for differences in conformation, hydration, and thermodynamic stability of RNA and DNA oligonucleotides. Additionally, the 2'-OH group plays a central role in RNA catalysis. This important group lies in the shallow groove of RNA, where it is involved in a network of hydrogen bonds with water molecules stabilizing RNA A-form duplexes. Structural and dynamical information on 2'-OH hydroxyl protons is essential to understand their respective roles. Here we report the 2'-OH hydroxyl proton assignments for a 30mer RNA, the HIV-2 transactivation region, in water using solution NMR techniques. We provide structural information on 2'-OH hydroxyl groups in the form of orientational preferences contradicting the paradigm that the 2'-OH hydroxyl typically points away from the ribose H1' proton.