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) (By similarity). 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). May also act as a protein lysine acetyltransferase by mediating acetylation of target proteins; such activity is however unclear in vivo and recent evidences suggest that ELP3 primarily acts as a tRNA acetyltransferase (By similarity). Involved in neurogenesis: regulates the migration and branching of projection neurons in the developing cerebral cortex, through a process depending on alpha-tubulin acetylation (PubMed:19185337). Required for acetylation of GJA1 in the developing cerebral cortex (PubMed:28507509). 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, ELP2, ELP3, ELP4, ELP5 and ELP6. ELP1, ELP2 and ELP3 form the elongator core complex. Interacts with alpha-tubulin. Ubiquitously expressed in blastocysts and 10.5 dpc embryos (PubMed:27476491). Expression increases during embryonic stem cell maintenance differentiation (PubMed:27476491). Tyrosine-phosphorylated. Also serine/threonine-phosphorylated. Embryonic lethality by 12.5 dpc caused by severe growth retardation (PubMed:27476491, PubMed:29415125). Conditional deletion in adults is also lethal (PubMed:29415125). 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. The relevance of the protein lysine acetyltransferase activity is unclear (By similarity). The publication reporting acetylation of GJA1 does not provide direct evidence of lysine acetyltransferase activity of ELP3 (PubMed:28507509).