Required for pre-mRNA splicing as component of the spliceosome, including pre-catalytic, catalytic and post-catalytic spliceosomal complexes (PubMed:25092792, PubMed:28076346, PubMed:28502770, PubMed:28781166, PubMed:29301961, PubMed:29360106, PubMed:29361316, PubMed:30315277, PubMed:30705154). Component of the U5 snRNP and the U4/U6-U5 tri-snRNP complex, a building block of the spliceosome (PubMed:16723661). As a component of the minor spliceosome, involved in the splicing of U12-type introns in pre-mRNAs (Probable). {ECO:0000269|PubMed:16723661, ECO:0000269|PubMed:25092792, ECO:0000269|PubMed:28076346, ECO:0000269|PubMed:28502770, ECO:0000269|PubMed:28781166, ECO:0000269|PubMed:29301961, ECO:0000269|PubMed:29360106, ECO:0000269|PubMed:29361316, ECO:0000269|PubMed:30315277, ECO:0000269|PubMed:30705154, ECO:0000305|PubMed:33509932}. This is the function of EFTUD2 (elongation factor Tu GTP binding domain containing 2, Ensembl gene identifier ENSG00000108883).