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Oliner et al., 1992). In addition, it is also thought to function as a regulator of p53 function. This stems from evidence that the MDM2 protein forms oligomeric complexes with the p53 protein in vivo and in vitro (Momand et al., 1992;Oliner et al., 1992) and when experimentally overexpressed inhibits the transactivating capability of p53 (Momand et al., 1992). This inhibition is thought to result from the MDM2 protein binding directly to the acidic activation domain of p53, concealing it from the transcriptional machinery (Oliner et al., 1993). Apart from its role as a p53 regulator, MDM2 also has oncogenic properties, as evident from transfection studies in which MDM2 overexpression was found to increase the tumorigenic potential of NIH3T3 and Rat2 cells (Fakharzadeh et al., 1991) and to overcome wild-type p53 suppression of transformed cell growth (Finlay, 1993 Following hybridisation with a [a-32PJdCLTP-labelled human MDM2 cDNA probe (C14-2), the membranes were exposed to intensifying screens for 2-10 days at -70°C. The blots were subsequently reprobed with the pDCCl.65 probe, which