An immunochemical study of localization of some nuclear matrix proteins in the composition of perinucleolar chromatin

Abstract

In nuclei of interphase pig embryo kidney cells (PEK), intense fluorescence of fluorochrome DAPI is observed at the periphery of nucleoli in regions of perinucleolar chromatin as a brightly fluorescing rim. In interphase cells, antibodies to proteins with molecular masses of 27, 38, 40, 50, and 65 kDa obtained from sera of patients with autoimmune diseases stain only nuclei as small accumulations or granules. These antibodies do not stain nucleoli themselves, but they are revealed at their periphery as a brightly fluorescing circle in the zone of the perinucleolar chromatin. Antibodies to the nucleolar proteins fibrillarin and B23 specifically stain only nucleoli. In nuclei, after removal of histones and DNA (nuclear protein matrix (NPM)), the protein fibrillarin is distributed uniformly throughout the volume of residual nucleoli, while the protein B23 is revealed only at their periphery where the perinucleolar chromatin is located. Antibodies to proteins with molecular masses of 40, 50, and 65 kDa are connected with the periphery of residual nucleoli and are spread throughout the cell karyoplasm as small accumulations. Antibodies to proteins with molecular masses of 27 and 38 kDa are connected only with the periphery of residual nucleoli. It has been established that the nuclear matrix proteins with molecular masses of 27, 38, 40, 50, and 65 kDa, as well as the protein B23, exist in the composition of the perinucleolar chromatin, which may be a special chromosomal domain associated with nucleolus functioning.