Distinct nuclear assembly pathways for lamins A and C lead to their increase during quiescence in Swiss 3T3 cells

Gareth E Pugh, Philip J Coates, E Birgit Lane, Yves Raymond, Roy A Quinlan

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    The expression of A-type lamins coincides with cell differentiation and as A-type lamins specifically interact with chromatin, a role in the regulation of differential gene expression has been suggested for A-type lamins. Using the mouse Swiss 3T3 cell line as a model, the change in two A-type lamins, lamins A and C, during cellular quiescence has been investigated. This well established model system mimics the first stages of differentiation when cells exit the cell cycle. In fact, quiescence in Swiss 3T3 cells was accompanied by a significant increase (2.6-fold) in lamin A protein levels and a smaller but reproducible increase (1.4-fold) in lamin C. These effects were fully reversible upon restimulation of the cells with serum. No effect upon lamin B levels was observed. Conversely, levels of A-type lamin mRNA decreased markedly as a result of quiescence suggesting transcriptional mechanisms are involved in the change in levels of lamins A and C. No difference in the incorporation of microinjected human lamin A into nuclei of quiescent or proliferating cells was observed. These data suggest A-type lamin binding sites were not limiting and indicated little difference between A-type lamin assembly mechanisms in quiescent and proliferating cells. The data did demonstrate lamin A and lamin C incorporation into the nuclear lamina proceeded by different pathways when microinjected in Swiss 3T3 cells. The incorporation of recombinant lamin C into the nuclear lamina was delayed compared to lamin A and proceeded via intranuclear foci. Such foci were not seen with microinjected lamin A. Instead, recombinant lamin A was rapidly (
    Original languageEnglish
    Pages (from-to)2483-2493
    Number of pages11
    JournalJournal of Cell Science
    Issue number19
    Publication statusPublished - 1997


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