CENP-B

Autoantibodies to centromeric proteins in the sera of patients with scleroderma were first described in 1980. Subsequent studies confirmed that anti-centromere antibodies (ACA) were most often found in patients with a limited form of systemic sclerosis previously referred to as CREST syndrome. These autoantibodies are also often detected in sera from patients with Raynaud’s phenomenon and occasionally in other rheumatic diseases such as systemic lupus erythematosus, Sjögren’s syndrome, and rheumatoid arthritis.  ACA have also been reported to occur with high prevalence in patients with primary biliary cirrhosis, in patients with malignancies and occasionally in normal individuals.

Although at least 9 proteins are known to be associated with the centromere complex, CENP-B is normally considered to be the major centromere antigen, since autoantibodies to this protein were found to be present at high titres in all ACA sera while titres of antibodies directed at two other centromere antigens (CENP-A, CENP-C) were often much lower. CENP-B is a dimer composed of two 80-kDa subunits which binds specifically to the 17bp CENP-B box sequence that is required for the formation of a functional centromere and is located within chromosomal α-satellite DNA . CENP-B may therefore function as a trans-acting factor that regulates the formation or centromere-specific chromatin on the α-satellite DNA repeat at the nucleosome assembly level.

Autoantibodies have been reported to bind to at least 3 different epitope regions of CENP B however the 60 amino acid C-terminal region appears to constitute the major autoimmune epitope.

 

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