U2 auxiliary factor small subunit (IPR009145)

Short name: U2AF_small

Overlapping homologous superfamilies

Family relationships



The U2 small nuclear ribonucleoprotein auxiliary factor (U2AF) is a heterodimeric splicing factor composed of a large and a small subunit [PMID: 12374752]. The large U2AF subunit recognises the intronic polypyrimidine tract, a sequence located adjacent to the 3' splice site that serves as an important signal for both constitutive and regulated pre-mRNA splicing. The small subunit interacts with the 3' splice site dinucleotide AG and is essential for regulated splicing. The subunits shuttle continuously between the nucleus and the cytoplasm via a mechanism that involves carrier receptors and is independent of binding to mRNA. Both subunits contain an arginine/ serine-rich (RS) domain, which acts as a nuclear localisation signal. Furthermore, the presence of an RS domain on either subunit is sufficient to trigger the nucleocytoplasmic import of the heterodimeric complex [PMID: 1824937, PMID: 2531895, PMID: 9632785].

The human form of the U2 auxiliary factor small subunit, hU2AF35, contains a degenerate RNA recognition motif (RRM) and a C-terminal RS domain. The murine form has been shown to be genomically imprinted with monoallelic expression from the paternal allele. However, this is not the case in humans [PMID: 8630064].

GO terms

Biological Process

GO:0000398 mRNA splicing, via spliceosome

Molecular Function

GO:0003723 RNA binding

Cellular Component

GO:0089701 U2AF

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.