ALTERATIONS OF EXPRESSION OF THE CYTOSKELETON AFTER IMMORTALIZATION OF HUMAN FIBROBLASTS

Human diploid fibroblasts (HDF) have a limited in vitro lifespan of po pulation doubling level (PDL) 50-70. The molecular mechanism underlyin g cellular senescence and immortalization is not thoroughly understood . It has been reported that the cytoskeleton has diverse functions and may have a role in growth regulation through association with other c ellular components. To shed light on the relationship between function s of the cytoskeleton and senescence or immortalization, we investigat ed the alterations in gene expression after immortalization and measur ed the amounts of mRNAs for talin, vinculin, alpha-actinin, tropomyosi n 1 (TM1), vimentin, lamin A and C, and alpha-tubulin by slot blot and Northern blot analyses. We found that the mRNAs for vinculin and vime ntin were reduced and the mRNA for lamin A was increased in immortaliz ed cells. We also studied the cytoskeletal protein levels and their in tracellular distributions by Western blot analysis and immunostaining. Most of the proteins studied behaved in a way similar to the mRNAs th rough senescence and immortalization. Vinculin, tropomyosins and vimen tin showed their altered distributions in immortalized cells.