RNA modification enzyme TruB is a tRNA chaperone

RNAs are intimately involved in numerous cellular functions such as gene expression. Typically, RNAs adopt a 3D fold, and their sequences may be chemically altered to contain modified nucleotides such as pseudouridines. There are many RNA modification enzymes, but often their cellular functions remain unknown. In this proof-of-principle study, we show that the tRNA pseudouridine synthase TruB is a tRNA chaperone. In contrast to its modification activity, the ability of TruB to fold tRNA is critical for cellular fitness. It is likely that other modification enzymes and RNA-binding proteins act as RNA chaperones increasing the efficiency of RNA maturation. This connection of RNA modification with RNA folding may have arisen during the evolution from an RNA to a ribonucleoprotein world.