Fig. 4

Classes of the identified tRNA fragments (tRFs) and proposed mechanism of their biogenesis. a Contribution of particular tRF classes to the entire pool of tRNA derivatives. b Schematic representation of the tRFs with frequencies that exceeded 5% of all tRNA derivatives. tRFs are depicted in red (for fragments containing either the 5’ or 3’ end of the parental RNA) or in blue (for fragments cut from both ends), and the lost fragments of parental RNA are in gray. c Two-step mechanism of tRFΔ biogenesis. Following a primary cut in a single-stranded region, the resultant fragments can either remain base-paired or dissociate. If the first occurs, the overall fold of the RNA is retained, and a secondary cut takes place within a single-stranded region. In the case of dissociation, the fragments undergo structural rearrangement, which can render the original stems single stranded and thus accessible for a secondary cut. tRFs are depicted in red (for fragments containing either the 5’ or 3’ end of the parental RNA) or in blue (for fragments cut from both ends), and lost fragments of parental RNA are in gray