Analysis of the mi‐2 autoantigen of dermatomyositis

• Published in: Arthritis and rheumatism 1995-01, Vol.38 (1), p.123-128
• Main Authors: Nilasena, David S., Trieu, Edward P., Targoff, Ira N.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases; Antigens - chemistry; Autoantibodies - immunology; Autoantigens - blood; Autoantigens - chemistry; Autoantigens - isolation & purification; Biological and medical sciences; Dermatomyositis - blood; Dermatomyositis - immunology; DNA Helicases; Humans; Immunoblotting; Medical sciences; Mi-2 Nucleosome Remodeling and Deacetylase Complex; Molecular Weight; Precipitin Tests; Proteins - analysis; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis
• ISSN: 0004-3591; 1529-0131
• DOI: 10.1002/art.1780380119

Objective. To determine the biochemical structure and antigenic components of Mi‐2 autoantigen, the target of autoantibodies in 15–20% of dermatomyositis patients. Methods. Immunoprecipitation from 35S‐labeled HeLa cell extract, immunoblotting, and purification from bovine thymus by immunoaffinity chromatography. Results. All 46 sera that had anti–Mi‐2 autoantibodies demonstrated by immunodiffusion immunoprecipitated a major protein of ∼︁240 kd. Additional proteins of 200, 150, 72, 65, 63, 50, and 34 kd appeared to be part of the antigen. Fractions of purified bovine Mi‐2 with antigenic activity showed high molecular weight bands comparable with immunoprecipitated HeLa Mi‐2. Twenty‐four of 47 anti–Mi‐2 positive sera reacted with the 240‐kd protein by immunoblot against anti–Mi‐2 immunoprecipitates. Conclusion. Mi‐2 antigen consists of multiple proteins, of which the 240‐kd protein appears to be the major reactive component.