A single-stranded architecture for cotranscriptional folding of RNA nanostructures.

Artificial DNA and RNA structures have been used as scaffolds for a variety of nanoscale devices. In comparison to DNA structures, RNA structures have been limited in size, but they also have advantages: RNA can fold during transcription and thus can be genetically encoded and expressed in cells. We introduce an architecture for designing artificial RNA structures that fold from a single strand, in which arrays of antiparallel RNA helices are precisely organized by RNA tertiary motifs and a new type of crossover pattern. We constructed RNA tiles that assemble into hexagonal lattices and demonstrated that lattices can be made by annealing and/or cotranscriptional folding. Tiles can be scaled up to 660 nucleotides in length, reaching a size comparable to that of large natural ribozymes.