cDNA cloning of a novel autoantigen targeted by a minor subset of anti-centromere antibodies

Using autoimmune serum from a patient with anti-centromere antibodies, we have identified and partially characterized a novel protein with a mol. wt of ≈ 27 kD (hereafter referred to as p27). A cDNA expression library was screened with this serum, and two overlapping inserts were isolated among three positive clones other than clones corresponding to centromere protein (CENP)-B and CENP-C. Analysis of the sequence showed an open reading frame of ≈ 0.6 kb encoding 199 amino acids with a predicted mol. wt of 21.5 kD. Immunoblotting analysis with bacterial recombinant p27 showed that ≈ 2% of anti-centromere antibody-positive patients had autoantibodies to p27, whereas only one of 215 autoimmune patients without anti-centromere antibodies reacted with the recombinant. All five cases with anti-p27 antibodies, who were diagnosed as having scleroderma and/or Sjögren's syndrome, showed internal organ involvement. Although affinity-purified anti-p27 human or mouse polyclonal antibodies failed to stain any cellular structures in an immunofluorescence study, the potential association of anti-p27 with anti-centromere antibodies suggests that this novel autoantigen might play a role in mitosis.