Stress-dependent changes in the properties of p53 complexes by the alternative translation product p53/47

p53 plays a key role in the cellular response to damage exposure and in preventing the development of human cancers. Activation of p53 results in changes in the expression of a large number of gene products. However, relatively little is still known how p53 activation differentiates between different types of damages in different types of tissues or how this triggers either an apoptotic response or cell cycle arrest and DNA repair. The p53 message is translated into two products with distinct activities and stabilities through alternative mechanisms of initiation. p53/47 is initiated 40 codons down stream of the full length p53 and does not include the binding site for the E3 ubiquitin ligase Mdm2 or the transactivation domain I but retains the capacity to form p53 hetero- and homo-oligomers. Here we report that p53/47 controls the folding, the oligomerisation and the post-translational modification of p53 complexes and that it diversifies p53 properties in a cell stress-dependent fashion. p21 expression, for example, is under normal conditions not affected by p53/47 but is induced 18-fold after treatment of cells with the DNA damaging drug doxorubicin. This is accompanied by the recruitment of p53/47 to the p21 promoter.