Plays a role in pre-mRNA splicing as component of the U5 snRNP and U4/U6-U5 tri-snRNP complexes that are involved in spliceosome assembly, and as component of the precatalytic spliceosome (spliceosome B complex). {ECO:0000269|PubMed:28781166, ECO:0000305|PubMed:10610776, ECO:0000305|PubMed:26912367}. This is the function of Ensembl gene identifier ENSG00000141759 (TXNL4A, thioredoxin like 4A).