*3.1.1 tiRNA*

The generation of tiRNA occurs when the stress-induced RNase angiogenin (Ang) cleaves mature tRNA at the anticodon loop [51]. This produces transcripts 31–40 nts long that are defined as either 5′ or 3′tiRNA depending of the presence of a 3′ or 5′ end at the anticodon loop respectively (**Figure 1B**). The production of Ang is mediated by the transcription factor hypoxia-inducible factor-1α (HIF-1α) and thus tiRNA generation is closely linked with cellular stress [52]. Accumulation of tiRNA is known to occur following oxidative stress, heat shock, UV radiation, hypoxia and starvation [53–56].
