RTCB Complex Regulates Stress-Induced tRNA Cleavage

Abstract

Under stress conditions, transfer RNAs (tRNAs) are cleaved by stress-responsive RNases such as angiogenin, generating tRNA-derived RNAs called tiRNAs. As tiRNAs contribute to cytoprotection through inhibition of translation and prevention of apoptosis, the regulation of tiRNA production is critical for cellular stress response. Here, we show that RTCB ligase complex (RTCB-LC), an RNA ligase complex involved in endoplasmic reticulum (ER) stress response and precursor tRNA splicing, negatively regulates stress-induced tiRNA production. Knockdown of RTCB significantly increased stress-induced tiRNA production, suggesting that RTCB-LC negatively regulates tiRNA production. Gel-purified tiRNAs were repaired to full-length tRNAs by RtcB in vitro, suggesting that RTCB-LC can generate full length tRNAs from tiRNAs. As RTCB-LC is inhibited under oxidative stress, we further investigated whether tiRNA production is promoted through the inhibition of RTCB-LC under oxidative stress. Although hydrogen peroxide (H2O2) itself did not induce tiRNA production, it rapidly boosted tiRNA production under the condition where stress-responsive RNases are activated. We propose a model of stress-induced tiRNA production consisting of two factors, a trigger and booster. This RTCB-LC-mediated boosting mechanism may contribute to the effective stress response in the cell.

ROS-induced ribosome impairment underlies ZAKα-mediated metabolic decline in obesity and aging

“…These may include tRNAs and initiation and elongation factors. Although we did not obtain evidence of oxidative damage to the latter, we corroborated recently published evidence of ROS-induced tRNA cleavage and fragmentation ( 43 ). In addition to representing a depletion of key translation components, these fragments, likely generated by the RNase angiogenin, are generally considered to be inhibitory to ribosomal function ( 41 , 42 ).…”

“…Angiogenin is a tRNA-cleaving RNase that is activated upon a multitude of cellular stress insults to produce translation-inhibiting tRNA fragments ( 41 , 42 ). Activation of angiogenin by menadione and ensuing tRNA cleavage was recently demonstrated ( 43 ). Although these effects may not be the only relevant ones, we conclude that ROS-inducing agents interfere with translation in vivo and in vitro and activate ZAKα and the RSR.…”

Nicked tRNAs are stable reservoirs of tRNA halves in cells and biofluids

“…Nevertheless, it should be considered that most of the enzymatic activities used in this work to repair anticodon-cleaved nicked tRNAs are present in human cells ( 54 , 55 ). Reversibility of stress-induced nicked tRNA formation in cellulo arises as an exciting possibility ( 56 ).…”

tRNA‐derived RNAs: Biogenesis and roles in translational control

“…However, it is still unclear whether oxidation of RNH1 is the principal mechanism of RNH1 dissociation. We have recently reported that there seem to be both oxidative stress‐dependent and ‐independent mechanisms of RNH1 dissociation (Akiyama, Takenaka, et al, 2022). Menadione‐induced RNH1 dissociation from ANG was completely abolished by an antioxidant N‐acetyl‐L‐cysteine, while sodium arsenite‐induced RNH1 dissociation was not affected at all, suggesting that sodium arsenite induces the dissociation of RNH1 in an oxidative stress‐independent manner.…”

“…We have recently reported that the RTCB ligase complex (RTCB-LC) negatively regulates tiRNA production (Akiyama, Takenaka, et al, 2022). Under normal conditions, RTCB-LC inhibits tiRNA production likely by sealing a cleaved site before the cleaved (so-called "nicked") tRNAs are separated into 5 0 -and 3 0 -tiRNAs.…”