Splicing factor 3B subunit 1 is a protein that in humans is encoded by the SF3B1 gene.

Function

This gene encodes subunit 1 of the splicing factor 3b protein complex. Splicing factor 3b, together with splicing factor 3a and U2 spliceosomal RNA, forms the U2 small nuclear ribonucleoproteins complex (U2 snRNP). The splicing factor 3b/3a complex binds pre-mRNA upstream of the intron's branch site in a sequence independent manner and may anchor the U2 snRNP to the pre-mRNA. Splicing factor 3b is also a component of the minor U12-type spliceosome. The carboxy-terminal two-thirds of subunit 1 have 22 non-identical, tandem HEAT repeats that form rod-like, helical structures. Alternative splicing results in multiple transcript variants encoding different isoforms.

Interactions

SF3B1 has been shown to interact with:

Clinical relevance

Mutations in this gene have been recurrently seen in cases of advanced chronic lymphocytic leukemia, myelodysplastic syndromes and breast cancer. SF3B1 mutations are found in 60%-80% of patients with refractory anemia with ring sideroblasts (RARS; which is a myelodysplastic syndrome) or RARS with thrombocytosis (RARS-T; which is a myelodysplastic syndrome/myeloproliferative neoplasm). There is also an emerging body of evidence to suggest implications of SF3B1 mutations being involved in orbital melanoma.