ALKBH1 is an RNA dioxygenase responsible for cytoplasmic and mitochondrial tRNA modifications. Issue 12 (2nd May 2017) - Kawarada, Layla
Abstract: ALKBH1 is a 2-oxoglutarate- and Fe 2+ -dependent dioxygenase responsible for multiple cellular functions. Here, we show that ALKBH1 is involved in biogenesis of 5-hydroxymethyl-2΄- O -methylcytidine (hm 5 Cm) and 5-formyl-2΄- O -methylcytidine (f 5 Cm) at the first position (position 34) of anticodon in cytoplasmic tRNA Leu, as well as f 5 C at the same position in mitochondrial tRNA Met . Because f 5 C34 of mitochondrial tRNA Met is essential for translation of AUA, a non-universal codon in mammalian mitochondria, ALKBH1 -knockout cells exhibited a strong reduction in mitochondrial translation and reduced respiratory complex activities, indicating that f 5 C34 formation mediated by ALKBH1 is required for efficient mitochondrial functions. We reconstituted formation of f 5 C34 on mitochondrial tRNA Met in vitro, and found that ALKBH1 first hydroxylated m 5 C34 to form hm 5 C34, and then oxidized hm 5 C34 to form f 5 C34. Moreover, we found that the frequency of 1-methyladenosine (m 1 A) in two mitochondrial tRNAs increased in ALKBH1 -knockout cells, indicating that ALKBH1 also has demethylation activity toward m 1 A in mt-tRNAs. Based on these results, we conclude that nuclear and mitochondrial ALKBH1 play distinct roles in tRNA modification.