Computational Design of Asymmetric Three-dimensional RNA Structures and Machines.

The emerging field of RNA nanotechnology seeks to create nanoscale 3D machines by repurposing natural RNA modules, but successes have been limited to symmetric assemblies of single repeating motifs. We present RNAMake, a suite that automates design of RNA molecules with complex 3D folds. We first challenged RNAMake with the paradigmatic problem of aligning a tetraloop and sequence-distal receptor, previously only solved via symmetry. Single-nucleotide-resolution chemical mapping, native gel electrophoresis, and solution x-ray scattering confirmed that 11 of the 16 miniTTR designs successfully achieved clothespin-like folds. A 2.55 [A] diffraction-resolution crystal structure of one design verified formation of the target asymmetric nanostructure, with large sections achieving near-atomic accuracy (< 2.0 [A]). Finally, RNAMake designed asymmetric segments to tether the 16S and 23S rRNAs together into a synthetic singlestranded ribosome that remains uncleaved by ribonucleases and supports life in Escherichia coli, a challenge previously requiring several rounds of trial-and-error.