p53 RNA interactions: new clues in an old mystery.

The p53 tumor suppressor protein is typically considered to be a sequence-specific DNA-binding transcription factor. However, reports over the last 15 years have described RNA binding by p53 in a variety of contexts, suggesting the possibility of new p53 functions. It is clear that p53-RNA interactions are mediated by a nucleic acid-binding domain of p53 independent of the sequence-specific core domain responsible for DNA recognition. Reports disagree on several aspects of the putative RNA interaction, including sequence specificity and biological relevance. Here we review the history and recent advances in the study of p53-RNA interactions. We argue that p53-RNA interactions are sequence nonspecific and depend on incomplete post-translational modification of the p53 C-terminal domain when the protein is expressed in heterologous systems. It is unknown what fraction of p53 protein exists in a state competent for RNA binding in vivo. Thus, potential physiological roles of p53-RNA interactions remain mysterious.