STRUCTURAL AND KINETIC-ANALYSIS OF P53-DNA COMPLEXES AND COMPARISON OF HUMAN AND MURINE P53

Sequence-specific DNA binding by p53 is dependent upon protein conform ation. The 1620(+) form correlates with wild type p53 suppressor funct ion and is a prerequisite for binding to the DNA consensus p53-CON in vitro. It has been reported that murine p53 changes conformation on in teraction with high affinity DNA target sequences and in the present S tudy we have analysed p53-DNA complexes using conformation-specific mo noclonal antibodies against p53. For murine p53 (mp53) we show (i) the 1620(+) form is retained and stabilised in complex,vith DNA, and (ii) the complexes are dissociated by the PAb1620 monoclonal antibody. In contrast, PAb1620 did not detect nor dissociate human p53-DNA complexe s nor did it interfere with complex formation. In competition experime nts murine p53 replaced human p53 (hp53) in p53-DNA complexes and this correlated with the greater lability observed for hp53-DNA complexes at a given temperature. Mixed human-murine p53 oligomers were competen t for DNA binding,vith an estimated affinity around 5x10(-10)M, simila r to that observed for either human or murine p53 alone, The potential significance of these observations is discussed in relation p53 funct ion in vivo.