tRFs: miRNAs in disguise.

tRFs and tiRNAs are two new classes of regulatory non-coding small RNAs that are derived from the cleavage of pre-existing tRNAs. tRFs are 18-22 nt long and are classified into the tRF-5, tRF-3, and tRF-1 series. Here, we discuss in detail the regulatory roles of tRFs in translation, viral infections, and carcinogenesis. Moreover, we have reviewed the association of tRFs with Argonaute proteins, including their potential to function as miRNAs. Interestingly, few miRNAs are generated from pre-existing tRNAs. Hence, tRNAs generate similar-sized tRFs and miRNAs, leading to misannotations due to cross mapping of tRFs and tRNA-derived miRNAs during deep sequencing data analysis. Therefore, it is important to catalogue the overlapping sequences between tRNA-derived miRNAs and tRFs. We have catalogued the miRNAs that overlap with tRFs sequences in humans using miRBase. We identified 20 tRNA-derived miRNAs that share sequences with tRFs. Of the 20 miRNAs, 5 miRNAs (miR-3182, miR-4521, miR-1260a, miR-1260b, and miR-7977) showed significant prediction scores. Furthermore, we have identified a lysine degradation pathway as a common regulatory pathway for miR-1260a, miR-1260b, and miR-3182 by using DIANA-mirPath.