Crystal Structure of a p53 Tumor Suppressor-DNA Complex: Understanding Tumorigenic Mutations

Abstract

Mutations in the p53 tumor suppressor are the most frequently observed genetic alterations in human cancer. The majority of the mutations occur in the core domain which contains the sequence-specific DNA binding activity of the p53 protein (residues 102-292), and they result in loss of DNA binding. The crystal structure of a complex containing the core domain of human p53 and a DNA binding site has been determined at 2.2 angstroms resolution and refined to a crystallographic R factor of 20.5 percent. The core domain structure consists of a beta sandwich that serves as a scaffold for two large loops and a loop-sheet-helix motif. The two loops, which are held together in part by a tetrahedrally coordinated zinc atom, and the loop-sheet-helix motif form the DNA binding surface of p53. Residues from the loop-sheet-helix motif interact in the major groove of the DNA, while an arginine from one of the two large loops interacts in the minor groove. The loops and the loop-sheet-helix motif consist of the conserved regions of the core domain and contain the majority of the p53 mutations identified in tumors. The structure supports the hypothesis that DNA binding is critical for the biological activity of p53, and provides a framework for understanding how mutations inactivate it.

Twenty years of p53 research: structural and functional aspects of the p53 protein

“…Moreover, the central part contains Cho et al (1994). The tetrahedrally coordinated zinc atom is shown.…”

Targeting gene expression to tumor cells with loss of wild-type p53 function

“…13,[27][28][29] The relevance of this transactivating ability to the tumor suppressor function of p53 is reflected by the fact that ϳ80% of natural genetic changes in TP53 are missense mutations, which are largely confined to its evolutionarily well-conserved and sequence-specific DNA binding central region. 30,31 Furthermore, ϳ30% of mutations are concentrated at several hot spots (e.g., 175r3h, 248r3w, 249r3s, and 273r3h), the original residues of which either directly contact the DNA or preserve the structural integrity of the domain required for DNA binding. 31 The overwhelming majority of mtp53 molecules have lost the DNA sequence-specific binding capacity necessary for p53 transactivation of gene expression, 27,28,32 demonstrating the importance of this property for tumor suppressor function.…”

“…30,31 Furthermore, ϳ30% of mutations are concentrated at several hot spots (e.g., 175r3h, 248r3w, 249r3s, and 273r3h), the original residues of which either directly contact the DNA or preserve the structural integrity of the domain required for DNA binding. 31 The overwhelming majority of mtp53 molecules have lost the DNA sequence-specific binding capacity necessary for p53 transactivation of gene expression, 27,28,32 demonstrating the importance of this property for tumor suppressor function. 33 p53 also suppresses the transcription of a number of cellular and viral genes with promoters that are devoid of the consensus sequence recognized by p53, including c-fos, c-jun, interleukin-6, 34 Hsp70, 14 proliferating cell nuclear antigen, 35 multidrug resistance gene (MDR1) 36 topoisomerase IIa, 37 and Bcl-2.…”

Spi-1 transgenic mice develop a clonal erythroleukemia which does not depend on p53 mutation

“…In human cancers, the most frequent mechanism which inactivates the wild-type p53 is point mutations that occur in`hot spots' located inside the evolutionary conserved regions (Soussi and May, 1996). Ninety per cent of the mutations reside in the DNA binding domain between amino acids residues 102 and 292 and result in the loss of the p53 ability to act as a transcriptional regulator (for review, Cho et al, 1994;Prives, 1994).…”