Involved in pre-mRNA splicing as a component of the splicing factor SF3A complex that contributes to the assembly of the 17S U2 snRNP, and the subsequent assembly of the pre-spliceosome 'E' complex and the pre-catalytic spliceosome 'A' complex. Involved in pre-mRNA splicing as a component of pre-catalytic spliceosome 'B' complexes, including the Bact complex. Component of splicing factor SF3A which associates with the splicing factor SF3B and a 12S RNA unit to form the mature 17S U2 small nuclear ribonucleoprotein complex (17S U2 snRNP). Identified in the spliceosome 'E' complex, a precursor of the spliceosome 'A' complex. Identified in the spliceosome 'A' and 'B' complexes. Identified in the spliceosome 'C' complex. Belongs to the SF3A2 family.