Identification of hnRNP P2 as TLS/FUS using electrospray mass spectrometry

Protein complexes assembled on mRNA precursors can be separated by gel filtration chromatography to yield spliceosomal and H complex fractions (Reed R, Griffith J, Maniatis T, 1988, Cell 53:949-961; Reed R, 1990, Proc Natl Acad Sci USA 87:8031-8035.). Here we use Nano electrospray mass spectrometry (Wilm M, Mann M, 1994, Int J Mass Spectrometry Ion Processes 136:167-180) to identify proteins complexed with Adeno-pre-mRNA in the H complex peak. Four of the major hnRNP proteins, A1, B1, C1, and G, were identified by database analysis based on peptide mass and sequence information. A fifth protein in the H complex peak, corresponding to hnRNP P2, is shown to be the product of the TLS/FUS gene. This was originally identified as a chimeric oncogene formed by the chromosome translocation t(12;16) that is responsible for myxoid liposarcoma. The involvement of hnRNP P2 in oncogenesis provides a clear example of the importance of hnRNP proteins in molecular disease.