Presence of tRFs in bacteria to human. (A) Frequency of the three types of tRF in different human cell lines. tRF alignments that start with the first or second base of tRNA were collated as tRF-5 and whose 3' end mapped to the 3' end of tRNA and have a CCA at their 3' end were categorized as tRF-3. tRFs whose 5' end matched with the first or second bases of the 3' trailer sequence of a tRNA were categorized as tRF-1. The number of tRF-5, tRF-3 and tRF-1 mapped in each cell line was normalized with the total number of reads in the analyzed library. (B) Shows the frequency of tRF-5, tRF-3 and tRF-1 in mouse embryonic stem cells, mouse cell line NIH3T3, D. melanogaster, C. elegans, S. cerevisiae, S. pombe and R. sphaeroides. (C) tRF expression in different mouse tissues and embryonic stem cells (ESC).