U2AF35, U2AF65, and U2 snRNP splicing and complexing assay. Nuclear extracts were prepared from HEK293T cells expressing either mEGFP-U2B, mEGFP-SF3A3 or both mEGFP-U2AF65 and mCherry-U2AF35. The absolute and relative levels of functional labeled protein and their extent of dimerization were measured using Western blotting after affinity purification on RNA and single-molecule methods. OriGene TP790040 served as an mCherry concentration standard. Figure cited from Nucleic Acids Res, PMID: 27683217