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 transcr iption. In this study, we investigated the requirement of the carboxyl (C)- or amino (N)-terminal domain of p53 for the binding and transact ivation of two DNA elements, p53CON and the ribosomal gene cluster (RG C). Three human p53 mutants with deletion in either the C-terminus or N-terminus were used. Mobility-shift assays showed that the oligomeriz ation-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 PA b1801. Also, the transient transfection assays showed that the mutant p53(1-326) activated p53CON-mediated transcription. However, this muta nt failed to bind the RGC element and was unable to activate RGC-media ted transcription. Thus, the requirement of the C-terminal region of p 53 for DNA binding and transcription activation varies with the p53-bi nding DNA element under study. In contrast, the N-terminus of p53 cont ains a common transcription activation domain: deletion of the 80 or 1 59 N-terminal amino acids inactivated both p53CON- and RGC-mediated tr ansactivation. Furthermore, mobility-shift assays did not detect any b inding to p53CON and RGC by either of the two N-terminal-deletion muta nts. These results suggest that the N-terminus of p53 affects DNA bind ing.