p19ARF links the tumour suppressor p53 to Ras

Palmero, Ignacio; Pantoja, Cristina; Serrano, Manuel

doi:10.1038/25870

Cited by 567 publications

(422 citation statements)

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“…2f). Furthermore, expression of oncogenic Ras, which induces p19 ARF and p53 in early passage 20% oxygen MEFs 16 , induced p19 ARF and p53 in both early and later passage 3% oxygen MEFs (Fig. 2g).…”

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confidence: 92%

Oxygen sensitivity severely limits the replicative lifespan of murine fibroblasts

et al. 2003

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Most mammalian cells do not divide indefinitely, owing to a process termed replicative senescence. In human cells, replicative senescence is caused by telomere shortening, but murine cells senesce despite having long stable telomeres 1 . Here, we show that the phenotypes of senescent human fibroblasts and mouse embryonic fibroblasts (MEFs) differ under standard culture conditions, which include 20% oxygen. MEFs did not senesce in physiological (3%) oxygen levels, but underwent a spontaneous event that allowed indefinite proliferation in 20% oxygen. The proliferation and cytogenetic profiles of DNA repair-deficient MEFs suggested that DNA damage limits MEF proliferation in 20% oxygen. Indeed, MEFs accumulated more DNA damage in 20% oxygen than 3% oxygen, and more damage than human fibroblasts in 20% oxygen. Our results identify oxygen sensitivity as a critical difference between mouse and human cells, explaining their proliferative differences in culture, and possibly their different rates of cancer and ageing.Replicative senescence limits the proliferation of many cell types in culture and in vivo 2 .Human cells senesce replicatively largely because telomeres -DNA structures that cap chromosome ends -shorten and malfunction when replicated in the absence of telomerase, which most human cells do not express 1 . Senescent cells adopt a distinctive morphology and pattern of gene expression 2,3 , a phenotype also induced by telomere-independent events 2,4 such as DNA damage and activation of certain oncogenes. The senescence response is thought to suppress cancer 2 .MEFs are used widely in the study of replicative senescence, despite notable differences between human and rodent cells 1,2 . MEFs spontaneously overcome replicative senescence (immortalization) 5,6 , whereas human fibroblasts rarely do so. Moreover, MEF senescence relies predominantly on the p19 ARF /p53 tumour suppressor pathway, whereas human fibroblasts require loss of both p53 and retinoblastoma (Rb) tumour suppressor functions for Correspondence should be addressed to: J.C. (jcampisi@lbl.gov). Note: Supplementary Information is available on the Nature Cell Biology website. COMPETING FINANCIAL INTERESTSThe authors declare that they have no competing financial interests. Here, we compared the phenotypes of senescent mouse and human fibroblasts. We cultured MEFs from C57Bl/6 (or FVB; data not shown) mice under standard conditions, which include atmospheric (20%) oxygen (Fig. 1a). As expected 5 , the cells grew well for approximately 1 week (2-3 population doublings) before proliferation began to decline. After 4-5 weeks (8-10 population doublings), the cultures senesced (arrow), showing no change in cell number for more than 1 week and a senescent morphology. Proliferation eventually resumed, owing to outgrowth of immortal variants 5 . HHS Public AccessWe monitored the capacity for DNA synthesis at each passage by labelling cells with 3 Hthymidine for 3 days and counting radiolabelled nuclei. As reported 9 , the percentage of labelled nuclei d...

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confidence: 92%

Oxygen sensitivity severely limits the replicative lifespan of murine fibroblasts

et al. 2003

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“…The central role of ARF in inducing p53 by dominant oncogenes is underscored by the ®nding, in these studies, that oncogenes are unable to induce p53 and its downstream responses in ARF-null cells, while reintroduction of ARF restores oncogene responsiveness. Both p16 INK4A and ARF are essential for the activation of p53 and p53-dependent premature senescence in response to activated Ras or constitutively active MEK (MAP and ERK kinase, a downstream component of the MAP kinase pathway) (Lin et al, 1998;Palmero et al, 1998). Ras promotes uncontrolled proliferation and transformation in cells lacking either p53 or p16 INK4A , underscoring the involvement of both products of the INK4A gene in Ras responsiveness.…”

Section: Induction Of P53 By Uv: Variations On a Themementioning

confidence: 98%

Mechanisms of switching on p53: a role for covalent modification?

1999

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The p53 protein plays a pivotal role in activating and integrating adaptive cellular responses to a wide range of environmental stresses. Activation of p53 can occur by di erent molecular routes, depending on the nature of the activating signal. Central to the activation process, by whichever route, is the destabilization of the p53-MDM2 interaction. The molecular mechanisms which activate p53 involve elements of post-translational modi®cation, protein stabilization and protein-protein interaction. Two central themes are emerging from recent work in this area. The ®rst is that there are common events in the p53 activation process among di erent activating pathways. The second is that activation involves not just a single molecular event such as disruption of the p53-MDM2 interaction, but a series of sequential events the nature of which is governed by the type of activating stimulus. This review summarizes our current knowledge of the p53 activation process in response to two stimuli, DNA damage and activated oncogenes, and considers the contribution made by multisite phosphorylation in determining the nature of the p53 response.

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“…By linking the Rb and p53 signaling pathways, ARF plays a central role in monitoring cellular proliferation (Lowe and Sherr, 2003). Usually expressed at hardly detectable levels, p14 ARF is rapidly upregulated upon expression of viral and cellular oncogenes (de Stanchina et al, 1998;Palmero et al, 1998;Zindy et al, 1998). Through physical stabilization of p53 via sequestration and subsequent proteasomal degradation of mdm-2 (Hdm-2 in humans), p14 ARF was shown to trigger the transcription and activity of p53-responsive genes such as p21 or bax (Stott et al, 1998;Weber et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Bak functionally complements for loss of Bax during p14ARF-induced mitochondrial apoptosis in human cancer cells

et al. 2006

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In contrast to the initial notion that the biological activity of p14 ARF strictly depends on a functional mdm-2/p53 signaling axis, we recently demonstrated that p14 ARF mediates apoptosis in a p53/Bax-independent manner. Here, we show that p14 ARF induces breakdown of the mitochondrial membrane potential and cytochrome c release before triggering caspase-9-and caspase-3/7-like activities in p53/Bax-deficient DU145 prostate cancer cells expressing wild-type Bak. Re-expression of Bax in these cells failed to further enhance p14 ARF -induced apoptosis, suggesting that p14 ARF -induced apoptosis primarily depends on Bak but not Bax in these cells. To further define the role of Bak and Bax in p14 ARF -induced mitochondrial apoptosis, we employed short interference RNA for the knockdown of bak in isogeneic, p53 wildtype HCT116 colon cancer cells either proficient or deficient for Bax. There, combined loss of Bax and Bak attenuated p14 ARF -induced apoptosis whereas single loss of Bax or Bak was only marginally effective, as in the case of DU145. Notably, HCT116 cells deficient for Bax and Bak failed to release cytochrome c and showed attenuated activation of caspase-9 (LEHDase) and caspase-3/caspase-7 (DEVDase) upon p14 ARF expression. These data indicate that p14 ARF triggers apoptosis via a Bax/Bakdependent pathway in p53-proficient HCT116, whereas Bax is dispensable in p53-deficient DU145 cells. Nevertheless, a substantial proportion of p14 ARF -induced cell death proceeds in a Bax/Bak-independent manner. This is also the case for inhibition of clonogenic growth that occurs, at least in part, through an entirely Bax/Bakindependent mechanism.

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p19ARF links the tumour suppressor p53 to Ras

Cited by 567 publications

References 2 publications

Oxygen sensitivity severely limits the replicative lifespan of murine fibroblasts

Oxygen sensitivity severely limits the replicative lifespan of murine fibroblasts

Mechanisms of switching on p53: a role for covalent modification?

Bak functionally complements for loss of Bax during p14ARF-induced mitochondrial apoptosis in human cancer cells

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