Bhatter, N.; Advani, V. M.; Takenaka, Y.; Lyons, S. M.; Akiyama, Y.; Anderson, P. J.; Ivanov, P.

Transfer RNAs (tRNAs) are the key adaptor molecules aiding protein synthesis. Hundreds of tRNA genes are found in the human genome but the biological significance of this genetic excess is still enigmatic. The tRNA repertoires are variable between tissues and cells as well as during development. Such variations can only be partially explained by the correlation to the physiological needs in protein production, e.g. by changes in the expression of tRNA isoacceptor sets (tRNAs charged with the same amino acid but bearing different anticodons). However, changes in the expression levels of individual isodecoders (tRNAs with the same anticodon) are less understood. Besides canonical functions in mRNA translation, tRNAs are implicated in non-canonical functions unrelated to protein synthesis. tRNAs are rich source of small non-protein coding RNAs called tRNA-derived RNAs (tDRs), which include tRNA-derived stress-induced RNAs (tiRNAs) formed in response to stress. Here, we show that tiRNAs derived from isodecoders different in a single nucleotide can also differ in their activities. Specifically, we show that isodecoder sets for tRNAHis-GTG, tRNAGly-GCC and tRNACys-GCA are cleaved by ribonucleases to yield 5-tiRNAs showing differential activity towards mRNA reporter translation. Our data propose a model where cleavage repurposes specific tRNA isodecoders for non-canonical functions.