Detection and characterization of muscle-specific nuclear proteins

To identify nuclear proteins related to muscle tissue specificity, we tried to prepare antibodies recognizing muscle-specific nuclear proteins. Taking advantage of the autoimmunity of some nuclear proteins, we prepared an antiserum against chick muscle nuclear proteins by injecting protein components of the nuclei isolated from chick breast muscles into breast muscle. Three proteins, named p30, p32, and p37, were detected with the antiserum in a two-dimensional SDS-PAGE pattern of the isolated nuclei. P30 and p32 were not detected in the nuclei of liver, brain, cardiac muscle, or slow type skeletal muscle (anterior latissimus dorsi). They were detected in those of fast type skeletal muscle (pectoralis major and semitendinosus) and smooth muscle (gizzard) at all developmental stages examined. On serial fractionation of muscle cell nuclei, they were detected in a fraction obtained after DNase I treatment of the sample, suggesting that the proteins weakly bind to chromatin. A homology search of amino acid sequences showed that there is no known protein similar to p32.