Involved in pre-mRNA splicing as a component of the splicing factor SF3B complex (Probable). SF3B complex is required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA (By similarity). Directly contacts the pre-mRNA branch site adenosine for the first catalytic step of splicing (By similarity). Enters the spliceosome and associates with the pre-mRNA branch site as part of the 17S U2 or, in the case of the minor spliceosome, as part of the 18S U11/U12 snRNP complex, and thus may facilitate the interaction of these snRNP with the branch sites of U2 and U12 respectively (By similarity). Component of splicing factor SF3B complex (PubMed:18981222). Component of the U11/U12 snRNPs that are part of the U12-type spliceosome (By similarity). Belongs to the SF3B6 family.