Cloning of a novel nucleolar guanosine 5'-triphosphate binding protein autoantigen from a breast tumor.
A cDNA clone encoding an immunoreactive autoantigen (Ngp-1) was isolated by screening lambda gt11 human ductal breast tumor expression libraries with autologous patient serum. The complete 2.3-kb nucleotide sequence of the cDNA was found to contain an open reading frame that could encode a protein of 731 amino acids. The predicted amino acid sequence contains a high concentration of charged amino acids in the carboxy terminal quarter of the molecule, three guanosine 5'-triphosphate (GTP)-binding protein motifs, and a consensus nuclear localization signal. The arrangement and spacing of the GTP-binding protein motifs indicate that Ngp-1 belongs to a newly described subfamily of GTPases. Except for the consensus motifs, neither nucleotide sequence, nor the predicted amino acid sequence of the Ngp-1 cDNA showed the slightest homology to any vertebrate gene product sequence listed in the databases. Northern blot analysis showed the 2.3-kb transcript to be ubiquitously expressed at relatively low levels in all human tissues tested, with the highest level of expression in the testes. Immunohistochemical analysis of tissue sections with affinity-purified antiserum raised against a recombinant Ngp-1 protein revealed that the antigen was exclusively localized to the nucleolus and nucleolar organizer regions in all cell types analyzed.
Racevskis
J
J
Department of Oncology, Montefiore and Albert Einstein Cancer Center, Bronx, New York 10467, USA.
Dill
A
A
Stockert
R
R
Fineberg
S A
SA
D000595:Amino Acid Sequence; D001323:Autoantibodies; D001324:Autoantigens / Q000235:genetics*; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000737:chemistry*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000276:immunology; D015723:Gene Library; D005820:Genetic Testing; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000276:immunology; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000235:genetics; D017422:Sequence Analysis, DNA
D001323:Autoantibodies; D001324:Autoantigens; D018076:DNA, Complementary; C104699:NGP-1 antigen, human; D009687:Nuclear Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D019204:GTP-Binding Proteins