The interaction of p53 with 3'-terminal mismatched DNA.
The diversity of p53 functions involves its interaction with sequence-specific, non-sequence-specific and various damaged sites in DNA. The preferential excision of misincorporated over correct nucleotides by the 3'→5' exonuclease activity of p53 provides a molecular basis for p53 involvement in the correction of the DNA replication errors. However, p53 exhibits variations in its comparative efficiency to excise different 3'-terminal mismatched nucleotides. To determine the importance of the binding capacity of the protein to various 3'-terminal damaged sites, we have examined the interaction of p53 with linear dsDNAs containing various 3'-terminal mismatches, employing a gel retardation assay. The data demonstrate the intrinsic 3'-terminal mismatched DNA binding capacity of p53. Since p53 binds directly to various 3'-terminal purine:pyrimidine and purine:purine mispairs to an equal extent, p53 can be considered as a general 3'-mismatched DNA binding protein. Apparently, 3'-terminal mismatched bases are structural element to which p53 can bind, that extends the spectrum of damage sites to which p53 may respond. The formation of the p53-mismatched DNA complex is independent of the sequence context. Thus, the dissimilarities in mispair excision efficiency are probably due to an inherent property of the p53 in excision of 3'-mismatched nucleotides by a bound protein. The results establish a framework for understanding the mechanism of cooperative interaction between p53 and exonuclease-deficient DNA polymerase (e.g. HIV-1 RT). Within the context of error-correction events, p53 by recognition and excision of 3'-mismatched nucleotides from DNA, may be involved in DNA repair, thus increasing the accuracy of DNA synthesis by DNA polymerases.
Bakhanashvili
Mary
M
Infectious Diseases Unit, Sheba Medical Center, Tel Hashomer, and the Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel. bakhanus@yahoo.com
Hizi
Amnon
A
Rahav
Galia
G
D020137:Base Pair Mismatch / Q000235:genetics; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D011485:Protein Binding; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D016159:Tumor Suppressor Protein p53; D004247:DNA