Anti-spliceosome associated factor 1, recruiter of U4/U6.U5 tri-snRNP antibodies are used for the immunodetection of the protein encoded by the SART1 gene. In humans, the canonical protein has a reported length of 800 amino acid residues and a mass of 90.3 kDa. Its subcellular localization is in the nucleus. It is ubiquitously expressed across many tissue types. A member of the SNU66/SART1 protein family, it is reported to play a role in mRNA splicing as a component of the U4/U6-U5 tri-snRNP, one of the building blocks of the spliceosome. Post-translational modifications have been described, including sumoylation. Other names for this target antigen include HAF, HOMS1, SART1259, SNRNP110, Snu66, U4/U6.U5 tri-snRNP-associated protein 1, IgE autoantigen, and Ara1. Gene orthologs have been identified in the mouse, rat, bovine, frog, zebrafish and chimpanzee species.