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Tolerance of high levels of wild-type p53 in transformed epithelial cells dependent on auto-regulation by mdm-2

Blaydes, J.P., Gire, V., Rowson, J. M. and Wynford-Thomas, D. (1997) Tolerance of high levels of wild-type p53 in transformed epithelial cells dependent on auto-regulation by mdm-2 Oncogene, 14, (15), pp. 1859-1868.

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A significant proportion of human cancers express high levels of p53 protein in the absence of an underlying mutation in the gene. Using transformed (Vh1) and non-transformed (FRTL-5) rat thyroid epithelial cell lines as a model, we have examined the mechanisms by which high levels of wild-type p53 may be tolerated. Stable transfection with p53-dependent reporter constructs demonstrated that the 'excess' wild-type p53 in Vh1 cells is not associated with a comparable increase in p53-dependent transcription (though the response to u.v. irradiation is retained). Mdm-2, which binds p53 and inhibits its transactivation activity, is overexpressed in Vh1 cells in the absence of gene amplification and in a p53-dependent manner. Furthermore disruption of p53-mdm-2 complex formation in Vh1 cells by microinjection of an antibody to the p53-binding domain of mdm-2 resulted in a dramatic increase in p53-dependent transcription. Since only a small proportion of the p53 in Vh1 cells was found to be in complex with mdm-2 (the majority of unbound protein being in a latent form), this suggests that mdm-2 selectively binds a pool of p53 that would otherwise be active as a sequence-specific activator of transcription. We suggest that, in some types of tumour, the 'sensitivity' of the p53-driven mdm-2 feedback loop may be sufficient to prevent free, active p53 reaching the level required for growth arrest or apoptosis, making them an ideal target for therapies designed to disrupt p53-mdm-2 interactions.

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Published date: 17 April 1997


Local EPrints ID: 150581
ISSN: 0950-9232
PURE UUID: 50000c8c-bef3-468b-b15b-0f6bca30e661

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Date deposited: 20 Jul 2010 14:15
Last modified: 18 Jul 2017 12:57

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Author: J.P. Blaydes
Author: V. Gire
Author: J. M. Rowson
Author: D. Wynford-Thomas

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