THE REQUIREMENT OF THE CARBOXYL-TERMINUS OF P53 FOR DNA-BINDING AND TRANSCRIPTIONAL ACTIVATION DEPENDS ON THE SPECIFIC P53 BINDING DNA ELEMENT

The p53 protein specifically binds DNA sequences and activates transcription. In this study, we investigated the requirement of the carboxyl (C)- or amino (N)-terminal domain of p53 for the binding and transactivation of two DNA elements, p53CON and the ribosomal gene cluster (RGC). Three human p53 mutants with deletion in either the C-terminus or N-terminus were used. Mobility-shift assays showed that the oligomerization-defective mutant p53(1-326), from which the final 67 C-terminal amino acids were deleted, retained the wild-type p53's ability to bind the p53CON element in the presence of anti-p53 monoclonal antibody PAb1801. Also, the transient transfection assays showed that the mutant p53(1-326) activated p53CON-mediated transcription. However, this mutant failed to bind the RGC element and was unable to activate RGC-mediated transcription. Thus, the requirement of the C-terminal region of p53 for DNA binding and transcription activation varies with the p53-binding DNA element under study. In contrast, the N-terminus of p53 contains a common transcription activation domain: deletion of the 80 or 159 N-terminal amino acids inactivated both p53CON- and RGC-mediated transactivation. Furthermore, mobility-shift assays did not detect any binding to p53CON and RGC by either of the two N-terminal-deletion mutants. These results suggest that the N-terminus of p53 affects DNA binding.