Nuclear lamina assembly, synthesis and disaggregation during the cell cycle in synchronized HeLa cells

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Abstract
The pattern of assembly, synthesis and disaggregation of the nuclear envelope-associated lamina in synchronized HeLa cells has been examined by means of immunofluorescence microscopy of cell preparations treated with antibody to lamina polypeptide LP67 or lamin B, using the nomenclature of Gerace and Blobel. During the cell cycle the distribution of lamina polypeptide varies dramatically. Three distinct stages can be detected with respect to its location and synthesis: Lamina reformation in late mitosis and the polarity of its appearance in the telophase cell can be perturbed by treatment with colcemid or low temperature so that lamina is induced to associate with metaphase and anaphase chromosomes. In the absence of spindle microtubules lamina reformation may proceed around the surface of whole chromosomes, leading to the formation of micronuclei in G1 cells. We propose that in the normal cell nuclear envelope formation at telophase is related to the terminal distribution of cytoskeleton structures such that lamina is laid down only on the outer surface of the telophase genome beginning at the telomeric chromosome ends adjacent to the remaining mitotic fibres of the cleavage furrow.