Analysis of the Mi-2 autoantigen of dermatomyositis.
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 approximately 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.


CONCLUSIONS
Mi-2 antigen consists of multiple proteins, of which the 240-kd protein appears to be the major reactive component.
Nilasena
D S
DS
Veterans Affairs Medical Center, Salt Lake City, Utah.
Trieu
E P
EP
Targoff
I N
IN
D000251:Adenosine Triphosphatases; D000941:Antigens / Q000737:chemistry; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D004265:DNA Helicases; D003882:Dermatomyositis / Q000097:blood* / Q000276:immunology; D006801:Humans; D015151:Immunoblotting; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex; D008970:Molecular Weight; D011233:Precipitin Tests; D011506:Proteins / Q000032:analysis
D000941:Antigens; D001323:Autoantibodies; D001324:Autoantigens; C115323:CHD4 protein, human; C045760:Mi-2 antibodies; D011506:Proteins; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex; D000251:Adenosine Triphosphatases; D004265:DNA Helicases