Catalytic tRNA acetyltransferase subunit of the elongator complex which is required for multiple tRNA modifications, including mcm5U (5-methoxycarbonylmethyl uridine), mcm5s2U (5-methoxycarbonylmethyl-2-thiouridine), and ncm5U (5-carbamoylmethyl uridine) (PubMed:20398216). In the elongator complex, acts as a tRNA uridine(34) acetyltransferase by mediating formation of carboxymethyluridine in the wobble base at position 34 in tRNAs (By similarity). Promotes organ development by modulating cell division rate (PubMed:20080602). Required for auxin distribution or signaling (PubMed:20080602). Required for meristem cell cycle activation at the time of germination (PubMed:23969312). Mediates the establishment of leaf polarity independently of AS2 and the ta-siRNA-related pathway (PubMed:21700721). Indirectly involved in negatively regulating the expression of genes that participate in UV-B responses, such as DNA repair enzymes and enzymes that participate in sunscreen pigment biosynthesis (PubMed:25907565). acetyl-CoA + H2O + S-adenosyl-L-methionine + uridine(34) in tRNA = 5'-deoxyadenosine + carboxymethyluridine(34) in tRNA + CoA + 2 H(+) + L-methionine Binds 1 [4Fe-4S] cluster. The cluster is coordinated with 3 cysteines and an exchangeable S-adenosyl-L-methionine. tRNA modification; 5-methoxycarbonylmethyl-2-thiouridine-tRNA biosynthesis. Component of the elongator complex which consists of ELP1/ELO2, ELP2, ELP3/ELO3, ELP4/ELO1, ELP5, and ELP6 (PubMed:20080602). Interacts with IYO (PubMed:21620701). Localized in euchromatin during interphase. Expressed in meristematic tissues of in roots, leaves, seedlings, cotyledons, floral buds and shoot apices (PubMed:15894610, PubMed:20080602, PubMed:23969312). Expressed in the shoot meristem and the emerging leaves immediately after germination (PubMed:23969312). In the root, expressed in the transition zone and the upper meristematic zone (PubMed:23969312). Slow growing rate associated with pale-green and downwardly curled narrow leaves and reduced root growth that results from a decreased cell division rate and a reduced apical dominance. Defect in tRNA wobble uridine modification. Filamentous leaves with abaxialized epidermis in AS2 defective plants. Belongs to the ELP3 family. The elongator complex was originally thought to play a role in transcription elongation. However, it is no longer thought to play a direct role in this process and its primary function is thought to be in tRNA modification. Truncated N-terminus.