The snRNP-free U1A (SF-A) complex(es): identification of the largest subunit as PSF, the polypyrimidine-tract binding protein-associated splicing factor

RNA. 1998 Dec;4(12):1493-9. doi: 10.1017/s1355838298981183.


We have previously shown that a specific monoclonal antibody prepared against the U1A protein, MAb 12E12, is unique in its ability to recognize a form of U1A which is not associated with the U1snRNP. This unique form of U1A, termed snRNP-free U1A or SF-A, was found to be complexed with a novel set of non-snRNP proteins (O'Connor et al., 1997, RNA 3:1444-1455). Here we demonstrate that the largest protein in these SF-A complex(es), p105, is the polypyrimidine-tract binding protein-associated factor (PSF), an auxiliary splicing factor. We show that PSF copurifies and co-immunoprecipitates with SF-A from 293T cell nucleoplasm and that it interacts with SF-A in vitro. In addition, we show that MAb 12E12 inhibits both splicing and polyadenylation in an in vitro coupled splicing and polyadenylation reaction. This suggests that SF-A and/or the SF-A complex(es) perform an important function in both processing reactions and possibly in last exon definition.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Centrifugation, Density Gradient
  • Glutathione Transferase / metabolism
  • Molecular Sequence Data
  • PTB-Associated Splicing Factor
  • Poly A / antagonists & inhibitors
  • Precipitin Tests
  • Protein Binding
  • RNA Splicing
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Ribonucleoprotein, U1 Small Nuclear / metabolism*


  • PTB-Associated Splicing Factor
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Ribonucleoprotein, U1 Small Nuclear
  • U1A protein
  • Poly A
  • Glutathione Transferase