Table 1.

Definition of several features of the most common tRNA-derived fragments.

Name and type	Length (nt)	Domain of origin	Endonucleases	Known Biological Functions
tRNA fragment 1 (tRF-1)	13-30	Generated from pre-tRNA processing of trailer sequence	RNase Z (ELAC2)	Gene silencing not sequence-dependent Inhibition of T cell activation Cancer biomarker Associated to cancer development Tumour suppression in response to oncogenic stress
tRNA fragment 3 (tRF-3)	13-30	Generated from mature tRNA by endonucleolytic 3ʹ-end cleavage in the TΨC loop	DICER No identified endonucleases responsible for TΨC loop cleavage	Gene and retrotransposon silencing Ribosome biogenesis Translation inhibition Enhance specific transcripts related to cancer Associated to cancer development and lymphoma progression Inhibition of T cell activation Increase cell viability Tumour suppression in response to oncogenic stress
tRNA fragment 5 (tRF-5)	13-30	Generated from mature tRNA by endonucleolytic 5ʹ-end cleavage close to the D loop	DICER No identified endonucleases responsible for D loop cleavage	Gene silencing miRNA-like target inhibition Translation inhibition Enhance virus replication Associated to cancer development and lymphoma progression Inhibition of T cell activation May act as immune signalling molecule Tumour suppression in response to oncogenic stress
3ʹ tRNA halves	30-40	Generated from mature tRNA by endonucleolytic cleavage in the anticodon loop. Start from the anticodon loop and terminate in the 3ʹ-end of mature tRNA	Angiogenin and Rny1	Translation inhibition Stress-induced granule formation Enhance virus replication Tumour suppression in response to oncogenic stress
5ʹ tRNA halves	30-40	Generated from mature tRNA by endonucleolytic cleavage in the anticodon loop. Start from the 5ʹ-end and terminate in the anticodon loop of mature tRNA	Angiogenin and Rny1	Translation inhibition Enhance transcripts involved in stress response Stress-induced granule formation Associated to cell motility decrement Associated to cancer progression