Figure 1.

The biogenesis of tRNA-derived small RNAs (tsRNAs) from mature transfer RNAs (tRNAs). (A) Processing and classification of tsRNAs derived from mature tRNAs. The cleavage of an RNase at the D-loop or T-loop of a tRNA can generate a 5′ or 3′ tsRNA, respectively. The 5′ tsRNA could be generated by DCR, while 3′ tsRNA could be produced by DCR or ANG. Other unknown RNases (?) might also participate in tsRNA generation. The tRNA halves are cleaved by Rny1 and angiogenin (ANG) in yeasts and mammals, respectively. (B) The conservation patterns of Rny1 and ANG in eukaryotes. Among the five representative species, ANG is only present in humans and mice. Although the homologous sequence of Rny1 can be found in all the five species, currently Rny1 is only demonstrated to be involved in the biogenesis of tRNA halves in yeasts.