Anticentromere antibodies bind to trout testis histone 1 and a low molecular weight protein from rabbit thymus.

Antibodies directed against centromeric chromatin characteristically occur in the sera of patients with the CREST variant of scleroderma. We have studied the in situ enzymatic sensitivity and solubility of the centromeric antigen and have isolated an antigenic moiety that reacts with anticentromere antibodies. The centromeric antigen in the human epithelial cell line, HEp-2, was sensitive to DNAase I and micrococcal nuclease but not affected by RNAase A, trypsin or amylase. It was insoluble in 0.15-4 M NaCl but was extracted from the HEp-2 cells by 4 M urea/2 M NaCl. Antigenic activity in a 4 M urea/2 M NaCl extract of rabbit thymus was demonstrated by immunoabsorption. Indirect immunofluorescence of the extract separated by polyacrylamide gel electrophoresis revealed a fluorescent band with a mol. wt of 33,000. Calf thymus and trout testis histone preparations were fractionated by gel electrophoresis and transferred by blotting techniques to diazobenzyloxymethyl cellulose paper for autoradiography. Anticentromere antibodies bound to and were absorbed by trout testis histone 1. We propose that the centromeric antigen may be a variant of histone 1 that is associated with condensed chromatin.