Yildirim, Ilyas Chakraborty, Debayan Disney, Matthew D. Wales, David J. Schatz, George C. Computational Investigation of RNA CUG Repeats Responsible for Myotonic Dystrophy 1 Myotonic Dystrophy 1 (DM1) is a genetic disease caused by expansion of CTG repeats in DNA. Once transcribed, these repeats form RNA hairpins with repeating 1×1 nucleotide UU internal loop motifs, r­(C<u>U</u>G)<sub>n</sub>, which attract muscleblind-like 1 (MBNL1) protein leading to the disease. In DM1 C<u>U</u>G can be repeated thousands of times, so these structures are intractable to characterization using structural biology. However, inhibition of MBNL1-r­(C<u>U</u>G)<sub>n</sub> binding requires a detailed analysis of the 1×1 UU internal loops. In this contribution we employ regular and umbrella sampling molecular dynamics (MD) simulations to describe the structural and thermodynamic properties of 1×1 UU internal loops. Calculations were run on a reported crystal structure and a designed system, which mimics an infinitely long RNA molecule with continuous C<u>U</u>G repeats. Two-dimensional (2D) potential of mean force (PMF) surfaces were created by umbrella sampling, and the discrete path sampling (DPS) method was utilized to investigate the energy landscape of 1×1 UU RNA internal loops, revealing that 1×1 UU base pairs are dynamic and strongly prefer the <i>anti</i>–<i>anti</i> conformation. Two 2D PMF surfaces were calculated for the 1×1 UU base pairs, revealing several local minima and three <i>syn</i>–<i>anti</i> ↔ <i>anti</i>–<i>anti</i> transformation pathways. Although at room temperature the <i>syn</i>–<i>anti</i> ↔ <i>anti</i>–<i>anti</i> transformation is not observed on the MD time scale, one of these pathways dominates the dynamics of the 1×1 UU base pairs in temperature jump MD simulations. This mechanism has now been treated successfully using the DPS approach. Our results suggest that local minima predicted by umbrella sampling calculations could be stabilized by small molecules, which is of great interest for future drug design. Furthermore, distorted GC/CG conformations may be important in understanding how MBNL1 binds to RNA C<u>U</u>G repeats. Hence we provide new insight into the dynamic roles of RNA loops and their contributions to presently incurable diseases. umbrella sampling calculations;DM 1 CUG;umbrella sampling;RNA CUG Repeats;GC;MD time scale;Myotonic Dystrophy 1 Myotonic Dystrophy 1;UU;CTG;DPS;temperature jump MD simulations;DNA;future drug design;MBNL;loop;form RNA hairpins;2 D PMF surfaces 2015-12-17
    https://acs.figshare.com/articles/media/Computational_Investigation_of_RNA_CUG_Repeats_Responsible_for_Myotonic_Dystrophy_1/2054574
10.1021/acs.jctc.5b00728.s004