Fig. 1From: Mechanisms of tRNA-derived fragments and tRNA halves in cancer treatment resistanceClassification of tRFs. TRFs include tRF-1, tRF-2, tRF-3, tRF-5, and i-tRF. tRF-1 is generated from the 3′-end of pre-tRNA. tRF-2 is a tRNA fragment containing an anti-codon loop generated by an unknown cleavage method. tRF-3 and tRF-5 are derived from the 3′- and 5′-ends of mature tRNAs, respectively. i-tRF originates from the internal region of mature tRNABack to article page