The tumor suppressor p53 is an important cell cycle regulating transcription factor which is the most mutated gene in human cancers1,2. Most of these p53 cancer mutations cause a single amino acid substitution in the DNA-binding domain, leading to continued expression of full length p53 protein with a single amino acid alteration. The most common of these p53 DNA-binding domain missense mutations, R175H, causes the protein to be highly destabilized and nonfunctional at physiological temperatures1,3,5,20. A pharmaceutical which can restore endogenous p53 function to R175H or any of these single amino acid mutations could have an enormous impact on our treatment of cancer. After developing a high throughput screen, we have discovered a small molecule which is able to stabilize the R175H DNA-binding domain and induce R175H-dependent cell cycle arrest in cancer cells. Our goal is to use structural and molecular techniques to understand the effects of this small molecule on mutant p53 and how it is able to restore its normal function. We are investigating the structural changes in R175H induced upon its binding using X-ray crystallography. This will allow us to understand the mechanism which allows it to stabilize and reactivate p53. Through this same structure of the small molecule bound to R175H we will also be able to gain insight into the molecular interactions which allow it to bind p53. With knowledge of these interactions, we and others can then begin to make tailored modifications to this molecular scaffold in order to improve its binding and efficacy. Studies are being done to determine if this small molecule is able to restore normal DNA-binding activity to R175H, or if the observed reactivation is through another mechanism. We are also exploring the effects of chemical analogs of this molecule on R175H and other common missense mutations. Based on our current data, we hypothesize that this small molecule is able to bind to the zinc-coordinating region of the p53 DNA-binding domain, stabilizing the protein-DNA interface and allowing this mutant to regain transcriptional activity. We anticipate that this small molecule and several of it analogs will be able to bind and restore function to other conformational p53 DNA-binding domain mutants.
The tumor suppressor p53 gene is the most mutated gene in human cancers1,2. This project involves understanding how a recently discovered small molecule is able to restore function to the most common p53 mutations. This knowledge will aid in further development of this small molecule as a potential anti-cancer therapeutic.
