Component of the 17S U2 SnRNP complex of the spliceosome, a large ribonucleoprotein complex that removes introns from transcribed pre-mRNAs (  ). The 17S U2 SnRNP complex (1) directly participates in early spliceosome assembly and (2) mediates recognition of the intron branch site during pre-mRNA splicing by promoting the selection of the pre-mRNA branch-site adenosine, the nucleophile for the first step of splicing ( , ). Within the 17S U2 SnRNP complex, SF3A3 is part of the SF3A subcomplex 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 (, ).
Subcellular locations: Nucleus speckle, Nucleus
Ubiquitous.