Monoclonal antibodies to the nuclear matrix of chick embryonal erythrocytes.

Monoclonal antibodies were prepared from mice that had been immunized with the nuclear matrix from chick embryonal erythrocytes. Seven stable clones were obtained by an ELISA that used nuclear lysate as the solid phase. Six clones of them reacted with the nuclear matrix, and one reacted with nuclear components other than the matrix. Immunoblotting showed that one clone recognized the 72K polypeptide, two clones recognized the 69K polypeptide and three clones recognized both the 69K and 44K polypeptides. Indirect immunofluorescence that used antibodies to the nuclear matrix showed homogeneous nuclear fluorescence in cultured chick embryonal fibroblasts, and intense fluorescence was present in the peripheral part of the nucleus in thin-sectioned chick embryos. Only weak nuclear fluorescence was seen in fibroblasts from humans and rats when two of the antibodies which recognized only 69K polypeptide were used. The rest of the antibodies to the nuclear matrix produced no nuclear fluorescence in human and rat fibroblasts. The metaphase-rich population of chick embryonal fibroblasts were stained diffusely over the entire cytoplasm, but not the chromosomes, when antibodies to the nuclear matrix were used. These results indicate that monoclonal antibodies we prepared are directed to the major proteins of the nuclear matrix that correspond to the lamin A and B defined in rat liver.