RNA can function as molecular chaperone for RNA folding

RNAs can mimic the information storage, replication and catalysis functions of DNAs and proteins, providing physical evidence for the widely accepted RNA world hypothesis that RNA alone constitutes earlier life forms. However, the currently found molecular chaperones for correcting RNA folding are proteins, which poses a question on whether RNA itself can avoid misfolding in the absence of proteins. Here, we report two examples that RNA/ssDNA strands can serve as molecular chaperones to assist the folding of RNA/ssDNA structures with complex intramolecular interactions. We found that these RNA chaperones can disrupt the misfolded double-hairpin structures, assisting them to refold into native single-hairpin structures, which is a typical catalytical assembly called catassembly. The refolding rate was increased by at least three orders of magnitude. The identification that RNA can function as molecular chaperone for RNA folding may expand our understanding on RNA molecular chaperone and provides clues to rational design of catassembler.