[Nuclear matrix-intermediate filament scaffold of cybrid cells crossed between rabbit reticulocytes and K562 cells]

To elucidate the role of the mammalian erythroid cytoplasmic factor on erythroid cell denucleation, cybridization of neo gene transferred rabbit reticulocytes with human K562 erythroleukemia cells was performed, the structure and composition of the nuclear matrix-intermediate filaments (NM-IF) system of the reticulocytes, K562 cells and the cybrids between them, the K-RRneo Cells, were studied by employing the techniques of selective extraction and whole mount electron microscopy. It was shown that regional condensation of nuclear matrix with a thinned nuclear lamina were seen in the cybrids, while the intermediate filaments exhibited a network pattern reorganization comparatively similar with those of reticulocytes but different from the radiation pattern of the K562 cells. SDS-PAGE and western blot analysis also revealed that the proteins affinity to vimentin antibody in the cybrids migrate in a pattern similar with that of the rabbit reticulocytes, both of them with only residual depolymerized vimentin complex but not the polymerized vimentin band of 55 kd. These results suggested that the factors in the cytoplasm of the rabbit reticulocytes might function through a mechanism of vimentin depolymerization or blockage of gene expression, which finally resulted in destruction of intermediate filaments that facilitates the expellation of nucleus from cytoplasm.