THE ROLE OF CDC2, CDC25 AND CYCLIN A GENES IN THE MAINTENANCE OF IMMORTALIZATION AND GROWTH ARREST IN A RAT EMBRYONIC FIBROBLAST CONDITIONAL CELL LINE

Authors

  • EFSTATHIOS S. GONOS,

    Corresponding author
    1. National Hellenic Research Foundation, Department of Biotechnology and Molecular Oncology, 48 Vas. Constantinou Ave. Athens, 11635, Greece
    2. Ludwig Institute for Cancer Research, Courtauld Building, 91 Riding House St, London, W1P 8BT, U.K.
      To whom correspondence should be addressed.
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  • DEMETRIOS A. SPANDIDOS

    1. National Hellenic Research Foundation, Department of Biotechnology and Molecular Oncology, 48 Vas. Constantinou Ave. Athens, 11635, Greece
    2. University of Crete, Medical School, Heraklion, Greece
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To whom correspondence should be addressed.

Abstract

Immortalization of rodent cells by oncogenes is a complex biological process which involves the abnormal regulation of genes who control cellular proliferation. The role of the cell cycle control genes cdc2, cdc25 and cyclin A in the maintenance of immortalization and in growth arrest was examined in the tsa14, a SV40 T antigen rat embryonic fibroblast conditional for growth cell line. Analysis of RNA expression showed minimal levels of cdc2 mRNA in both proliferating and growth-arrested tsa14 cells. In contrast, cyclin A mRNA was found downregulated in growth-arrested tsa14 cells, as well as in senescent primary rat embryonic fibroblasts (REFS). The ability of cdc2, or cdc25, or cyclin A genes to maintain the tsa14 immortal phenotype was also examined by electroporations of these genes into the tsa14 cells. Clones over-expressing the electroporated cdc2, or cdc25, or cyclin A, or combinations of these genes growth arrested at the non-permissive conditions similar to controls, thereby suggesting that the expression of these genes alone is insufficient for tsa14 maintenance of immortalization.

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