[The nucleoli matrix proteins with molecular masses 40 and 27 kDa are transported as peripheral chromosomal material]

Using immunofluoresence method, sera M-311 and K-30 obtained from patients with autoimmune disease were shown to stain interphase nuclei and the periphery of chromosomes. Western blotting revealed a polypeptide with mol. mass 27 kDa in serum K-30. Both proteins were localized in the karyoplasm. One of them (27 kDa) has a diffuse form and contains small granules, while the other (40 kDa) is in the form of small clearly outlined granules. Both proteins are also revealed around the nucleolar periphery, making a continental ring, while the main part of the nucleolus remains unstained. During pro- and metaphase, these proteins were associated with the chromosomal periphery: 27 kDa protein formed separate groups, and 40 kDa protein was seen over the whole chromosomal periphery. After nuclear and chromosomal decondensation, induced by hypotonic treatment (15% of culture medium solution), both antibodies stain diffusively interphase nuclei, but in mitotic cells they stained the surface of the swollen chromosomes. After chromatin recondensation in isotonic medium these proteins were localized similarly as in normal cells. Thus, both proteins maintained their association with the periphery of chromosomes. To reveal the nuclear protein matrix, cells were treated with 2M NaCl, DNAase and RNAase A. After this procedure, the antibodies stained only the nucleolar periphery, and no fluorescence in the karyoplasm was seen. It shows that of all the components of the nuclear protein matrix (lamina, internuclear network, residual nucleoli) only 27 and 40 kDa proteins are contained in the nucleolar rim. The data allow to suggest that the nucleolar matrix proteins may be transported to new cell nuclei as part of the peripheral chromosomal material likely as other nucleolar (fibrillarin, B-23, and others) or some non-nuclear components of the nuclear protein matrix are transported.