The function of DDX39A (DExD-box helicase 39A, Ensembl gene identifier ENSG00000123136) is as follows. Helicase that plays an essential role in mRNA export and is involved in multiple steps in RNA metabolism including alternative splicing (PubMed:33941617, PubMed:38801080). Regulates nuclear mRNA export to the cytoplasm through association with ECD (PubMed:33941617). Also involved in spliceosomal uridine-rich small nuclear RNA (U snRNA) export by stimulating the RNA binding of adapter PHAX (PubMed:39011894). Plays a role in the negative regulation of type I IFN production by increasing the nuclear retention of antiviral transcripts and thus reducing their protein expression (PubMed:32393512). Independently of the interferon pathway, plays an antiviral role against alphaviruses by binding to a 5' conserved sequence element in the viral genomic RNA (PubMed:37949067). {ECO:0000269|PubMed:15047853, ECO:0000269|PubMed:17548965, ECO:0000269|PubMed:32393512, ECO:0000269|PubMed:33941617, ECO:0000269|PubMed:37949067, ECO:0000269|PubMed:38801080}.