Figure 2.

Mechanisms of tRFs-mediated sequence-specific gene silencing or repression of translation initiation. A) tRF-5s and tRF-3s associate with AGO proteins and sequence-specifically silence mRNAs. Target sites are found typically at the 3ʹ UTR, but also distributed all over the respective mRNAs. B) 5′tiRNAs with a 5′ TOG motif form an R4G structure that is required to displace the translation initiation complex eIF4A/G/E from capped mRNAs repressing translation initiation in cells under stress or in stem cells (SCs). C) In human embryonic stem cells (hESCs), 5′tiRNAs with a 5′ TOG and Ψ at position 8 displace PABPC1 from the translation initiation complex repressing translation of capped mRNAs.