Fig. 1

Anti-SF3B1 autoantibody, XC24, was identified in HBx-transgenic HCC model mouse. a Purified XC24 monoclonal autoantibody analyzed by SDS-PAGE (NR, non-reduced; R, reduced sample; M, molecular weight marker); b FACS analysis of intracellular-stained tumor cell lines with XC24 (immortalized liver cell Chang cell, HepG2 and Hep3B hepatocellular carcinoma cells as well as non-hepatocellular carcinoma cells, including cervical (HeLa), prostate (LNCaP-LN3), breast (MCF7), colon (HT29), lung (A549 and H460) cancer cells and mouse neuronal cell (HT22); c Western blot analysis of specific antigen against XC24 TA autoantibody; d Protein identification by mass spectroscopic analysis. Tryptic digest peptides derived from proteins in three bands indicated as XC24 Ag were extracted and analyzed by mass spectrometry (Table 1); e Verification of XC24 antigen as SF3B1 by knockdown assay using siRNA. The transcripts of SF3B1 and HYOU1 in knockdown cells were examined by RT-PCR and the protein level of XC24 antigen was confirmed by western blot analysis; f Verification of XC24 autoantibody-specific antigen as SF3B1 by immunoprecipitation and western blot analysis. SF3B1 immunoprecipitated with a commercial rabbit anti-SF3B1 antibody was analyzed by western blotting with XC24 mouse monoclonal antibody or vice versa (Additional file 2: Fig. S1); g Immunofluorescence intracellular staining of tumor cells with anti-SF3B1 antibody or XC24 monoclonal antibody; h Western blot analysis of subcellular localization of XC24 antigen (Additional file 3: Fig. S2). GAPDH was used as a cytoplasmic marker and Lamin B1 was used as a nuclear marker