title: Novel nuclear autoantigen with splicing factor motifs identified with antibody from hepatocellular carcinoma.
abstract: A patient with liver cirrhosis who progressed to hepatocellular carcinoma was found to develop novel antinuclear antibodies. The serum was used to isolate full-length cDNA clones encoding related proteins of 530 amino acids (representative clone HCC1.4) and 524 amino acids (representative clone HCC1.3). Affinity-purified antibodies eluted from recombinant proteins recognized a 64-kD nuclear protein in Western blotting and decorated the nucleoplasm in a speckled-network fashion in immunofluorescence, colocalizing with antibodies to pre-mRNA splicing factor SC35 and uridine-rich small nuclear RNAs. The deduced amino acid sequence contained an arginine/serine-rich (RS) domain and three-ribonucleoprotein consensus sequence domains, two classes of motifs present in several splicing factors. A repeating octapeptide of Arg-Ser-Arg-Ser-Arg(Lys)-Glu(Asp)-Arg-Lys(Arg) was present in RS region of HCC1. This octapeptide sequence called RS-ERK motif was also found in splicing factors U2AF 35- and 65-kD proteins and 70-kD U1 small nuclear ribonucleoprotein. The molecular features and immunolocalization data suggest that the HCC1 autoantigen may be associated with splicing activities and are consistent with observations that autoantibody responses frequently target molecules involved in important cellular biosynthetic functions.
authors.affiliation: W. M. Keck Autoimmune Disease Center, Scripps Research Institute, La Jolla, California 92037.
authors.forename: H
authors.initials: H
authors.lastname: Imai
authors.forename: E K
authors.initials: EK
authors.lastname: Chan
authors.forename: K
authors.initials: K
authors.lastname: Kiyosawa
authors.forename: X D
authors.initials: XD
authors.lastname: Fu
authors.forename: E M
authors.initials: EM
authors.lastname: Tan
mesh_terms: D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000097:blood*; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000276:immunology*; D002451:Cell Compartmentation; D002460:Cell Line; D002467:Cell Nucleus / Q000276:immunology*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D008103:Liver Cirrhosis / Q000150:complications; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000276:immunology*; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000276:immunology*; D012261:Ribonucleoproteins / Q000235:genetics; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D017381:Spliceosomes; D000072668:Splicing Factor U2AF; D014018:Tissue Distribution
chemical_list: D001323:Autoantibodies; D018076:DNA, Complementary; C084105:HCC1 autoantigen; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D000072668:Splicing Factor U2AF; C000607494:U2AF2 protein, human