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| Subject Categories: Cell Cycle | Molecular Biology of Disease |
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| The EMBO Journal
(2003) 22, 4212–4222, doi:10.1093/emboj/cdg417 |
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| Reversal of human cellular senescence: roles of the p53 and p16 pathways |
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| Christian M. Beauséjour1, Ana Krtolica1, Francesco Galimi2, 3, Masashi Narita4, Scott W. Lowe4, Paul Yaswen1 and Judith Campisi1, 5 |
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1 Lawrence Berkeley National Laboratory, MS 84-171, 1 Cyclotron Road, Berkeley, CA 94720, USA 2 The Salk Institute, La Jolla, CA, USA 3 Department of Biomedical Sciences, University of Sassari Medical School, 07100 Sassari, Italy 4 Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA 5 Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, CA 94945, USA To whom correspondence should be addressed Judith Campisi, jcampisi@lbl.gov Received 29 November 2002; Revised 12 May 2003; Accepted 1 July 2003. |
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| Abstract |
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| Telomere erosion and subsequent dysfunction limits the proliferation of normal human cells by a process termed replicative senescence. Replicative senescence is thought to suppress tumorigenesis by establishing an essentially irreversible growth arrest that requires activities of the p53 and pRB tumor suppressor proteins. We show that, depending on expression of the pRB regulator p16, replicative senescence is not necessarily irreversible. We used lentiviruses to express specific viral and cellular proteins in senescent human fibroblasts and mammary epithelial cells. Expression of telomerase did not reverse the senescence arrest. However, cells with low levels of p16 at senescence resumed robust growth upon p53 inactivation, and limited growth upon expression of oncogenic RAS. In contrast, cells with high levels of p16 at senescence failed to proliferate upon p53 inactivation or RAS expression, although they re-entered the cell cycle without growth after pRB inactivation. Our results indicate that the senescence response to telomere dysfunction is reversible and is maintained primarily by p53. However, p16 provides a dominant second barrier to the unlimited growth of human cells. |
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| Keywords: cyclin-dependent kinase, pRB, RAS, senescence, telomerase |
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