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

p53 protein stability in tumour cells is not determined by mutation but is dependent on Mdm2 binding

“…Low levels of mutant p53 expressed in the presence of Mdm2 may not be su cient to block the transcription activation activity of the remaining wild-type protein, hence the importance of losing all active p53 expression in order to escape DNA damage induced surveillance. Several human tumours including sarcomas express wild-type p53 but have ampli®ed Hdm2 suggesting that wild-type p53 activity can be overcome in some circumstances by elevated levels of Hdm2 protein (Oliner et al, 1992;Blaydes et al, 1997 The requirement of the oligomerisation domain for regulation of p53 levels and Mdm2 binding is re¯ected in observations that two families with increased susceptibility to develop tumours show elevated expression of p53 in their normal tissues. Recently these patients were shown to have inherited a p53 allele with mutation in the oligomerisation domain Lomax et al, 1997;Varley et al, 1996) It will be interesting to determine whether these mutant proteins are able to escape Mdm2 mediated regulation of p53 levels.…”

“…CM-1 is a rabbit polyclonal raised against human p53 expressed in E. coli, and CM-5 is a rabbit polyclonal raised against mouse p53 expressed in E. coli (Midgley et al, 1995). MAbs 3G5, 4B2 and 2A10 (Chen et al, 1993) has been shown to block the interaction of p53 with Mdm2 (Blaydes et al, 1997).…”

“…Disruption of p53 ± Mdm2 interaction in MCF7 CMVHis169 mouse p53 cells stabilises p53 MCF7 CMVHis169 cells were micro-injected with a monoclonal antibody 3G5 which binds to Mdm2 and disrupts its binding to p53 (Blaydes et al, 1997). Cells co-stained with anti mouse IgG and CM-1 anti-Human p53 antiserum or CM-5 anti-Mouse p53 antiserum, showed strong nuclear staining for both the human and the mouse p53 protein only in the presence of 3G5 In control experiments where cells were injected with the antiMdm2 antibody 4B2, nuclear staining for p53 did not coincide with 4B2 staining (Figure 6c and d).…”

CtBPs promote mitotic fidelity through their activities in the cell nucleus

“…Microinjections were performed essentially as in Blaydes et al (1997), using an Eppendorf microinjection system (Femtojet and InjectMan N12, Eppendorf, Hamburg, Germany) mounted on a Zeiss Axiovert 200 microscope (Zeiss, Hertfordshire, UK) with heated stage. GST fusion proteins were at 1 mg/ml in phosphate buffered saline.…”

Strategies for manipulating the p53 pathway in the treatment of human cancer

“…This initial docking event can reduce p53 activity by blocking directly p53 protein interactions with transcriptional components. A second class of activating agents (2 ), including a p53-derived BOX-I peptide or a monoclonal antibody that binds to MDM2 protein at the MDM2/p53 interface (3G5 MAb) prevents MDM2 binding to p53 and liberates p53 to function as a transcription factor [89,90,92]. (iii) Blocking MDM2 ubiquitination of p53.…”