Splicing Factor 3A Subunit 3 (SF3A3)

The splicing factor 3a heterotrimer includes subunits 1, 2 and 3 and is necessary for the in vitro conversion of 15S U2 snRNP into an active 17S particle that performs pre-mRNA splicing. Subunit 3 interacts with subunit 1 through its amino-terminus while the zinc finger domain of subunit 3 plays a role in its binding to the 15S U2 snRNP. Two-dimensional gel analysis determined that the deduced 501-amino acid protein translates into a 61-kD protein, the same mass as native SF3A3 derived from purified spliceosomes. Northern blot analysis detected 3.2- and 2.1-kb transcripts in HeLa cells. Immunofluorescence microscopy localized SF3A3 to nuclear speckles. Binding analysis showed that SF3A3 interacts with SF3A1 through its N terminus and not through its C-terminal zinc finger-containing region.