InterPro domain: IPR034158

This entry represents the RNA recognition motif 1 (RRM1) of SF3B4, also termed pre-mRNA-splicing factor SF3b 49kDa (SF3b50), or spliceosome-associated protein 49 (SAP 49). SF3B4 is a component of the multiprotein complex splicing factor 3b (SF3B), an integral part of the U2 small nuclear ribonucleoprotein (snRNP) and the U11/U12 di-snRNP. SF3B is essential for the accurate excision of introns from pre-messenger RNA, and is involved in the recognition of the pre-mRNA's branch site within the major and minor spliceosomes [ 1 ]. SF3B4 functions to tether U2 snRNP with pre-mRNA at the branch site during spliceosome assembly [ 2 ]. It is an evolutionarily highly conserved protein with orthologues across diverse species.

SF3B4 contains two closely adjacent N-terminal RNA recognition motifs (RRMs). It binds directly to pre-mRNA and also interacts directly and highly specifically with another SF3B subunit called SAP 145 [ 3 ].

Mutations in the SF3B4 gene cause Nager syndrome, a form of acrofacial dysostosis which affects the development of the face, hands, and arms [ 3 ].

1. Molecular architecture of the multiprotein splicing factor SF3b. Science 300, 980-4
2. The prespliceosome components SAP 49 and SAP 145 interact in a complex implicated in tethering U2 snRNP to the branch site. Genes Dev. 8, 1974-83
3. Nager syndrome: confirmation of SF3B4 haploinsufficiency as the major cause. Clin. Genet. 86, 246-51