STEPWISE REASSEMBLY OF THE NUCLEAR-ENVELOPE AT THE END OF MITOSIS

The nuclear envelope consists of three distinct membrane domains: the outer membrane with the bound ribosomes, the inner membrane with the b ound lamina, and the pore membrane with the bound pore complexes. Usin g biochemical and morphological methods, we observed that the nuclear membranes of HeLa cells undergoing mitosis are disassembled in a domai n-specific manner, i.e., integral membrane proteins representing the i nner nuclear membrane (the lamin B receptor) and the nuclear pore memb rane (gp210) are segregated into different populations of mitotic vesi cles. At the completion of mitosis, the inner nuclear membrane-derived vesicles associate with chromatin first, beginning in anaphase, where as the pore membranes and the lamina assemble later, during telophase and cytokinesis. Our data suggest that the ordered reassembly of the n uclear envelope is triggered by the early attachment of inner nuclear membrane-derived vesicles to the chromatin.