Biogenesis and functions of aminocarboxypropyluridine in tRNA
Abstract Transfer (t)RNAs contain a wide variety of post-transcriptional modifications, which play critical roles in tRNA stability and functions. 3-(3-amino-3-carboxypropyl)uridine (acp 3 U) is a highly conserved modification found in variable- and D-loops of tRNAs. Biogenesis and functions of acp 3 U have not been extensively investigated. Using a reverse-genetic approach supported by comparative genomics, we find here that the Escherichia coli yfiP gene, which we rename tapT (tRNA aminocarboxypropyltransferase), is responsible for acp 3 U formation in tRNA. Recombinant TapT synthesizes acp 3 U at position 47 of tRNAs in the presence of S -adenosylmethionine. Biochemical experiments reveal that acp 3 U47 confers thermal stability on tRNA. Curiously, the Δ tapT strain exhibits genome instability under continuous heat stress. We also find that the human homologs of tapT , DTWD1 and DTWD2 , are responsible for acp 3 U formation at positions 20 and 20a of tRNAs, respectively. Double knockout cells of DTWD1 and DTWD2 exhibit growth retardation, indicating that acp 3 U is physiologically important in mammals.