Chromosome location of genes encoding human blood groups

In this study the transactivation potential and DNA binding activities of p53 protein were examined following exposure of A2780 cells, a human ovarian carcinoma cell line, to the DNA damaging agent, cis-diamminedichloroplatinum II (cisplatin). The endogenous murine double minute-2 gene (mdm-2) was used to monitor the ability of p53 to transactivate genes. Northern analysis showed an induction of mdm-2 mRNA upon cisplatin treatment. It was further demonstrated, using an RNase protection assay, that the p53-responsive, mdm-2 promoter (P2) was activated in cisplatin-treated A2780 cells. However, when p53 protein DNA binding activity was analyzed, there was no detectable increase in p53 sequence-specific DNA binding activity during the period of time following DNA damage when mdm-2 mRNA was induced. Instead the increase in p53 protein observed in nuclear, cytoplasmic, and whole cell extracts correlated with a latent conformation of p53 that lacked sequence-specific DNA binding activity. At low doses of cisplatin, these latent pools of p53 increased in parallel with mdm-2 gene activation and were detectable as early as 4 h following cisplatin treatment. In vitro attempts to convert the latent p53 into an active, sequence-specific DNA binding conformation were unsuccessful. Even though cisplatin-induced p53 lacked sequence-specific DNA binding activity, it does possess an increased affinity for cisplatin-damaged duplex DNA molecules. This represents the first identification where cisplatin treatment induces a p53 protein, lacking sequence-specific DNA binding but with an increased affinity for platinated DNA molecules.