Variable Mutations at the p53-R273 Oncogeic Hotspot Position Leads to Altered Properties

Mutations in p53 protein, especially in the DNA binding domain is one of the major hallmarks of cancer. The R273 position is a DNA contact position and has several oncogenic variants. Surprisingly, cancer patients carrying different mutant-variants of R273 in p53 have different survival rates indicating that the DNA contact inhibition may not be the sole reason for reduced survival with R273 variants. Here, we probed the structural properties of three major oncogenic variants of the R273: ([R273L], [R273H], and [R273C])p53. Using a series of biophysical, biochemical and theoretical simulation studies, we observe that these oncogenic variants of the p53 not only suffer a loss in DNA binding, but also show distinct structural stabilty, aggregation and toxicity profiles. [R273C]p53 shows maximum amyloidogenicity while [R273L]p53 shows maximum aggregation. Further probe in the aggregation mechanism show that [R273C]p53 aggregation is disulphide mediated whereas hydrophobic interactions dominate self-assembly in [R273L]p53. MD simulation studies clearly show that -helical intermediates are observed in [R273C]p53 whereas {beta}-sheets are observed for [R273L]p53. Our study indicates that each of the R273 variant has its own distinct property of stability and self-assembly, the molecular basis of which, may lead to different types of cancer pathogenesis in vivo. These studies will aid the design of therapeutic strategies for cancer using residue specific or process specific protein aggregation as target.\n\nStatement of significanceThe present work stems from an interesting observation that genetic mutations that results in switching of one amino acid to different variants at the same codon show different cancer cell progression. We are trying to understand the molecular reason behind the different gain-of-function opted by these variants. With the help of biophysical and biochemical experiments, and computational studies we have observed that the different thermal stability, unique mechanism of unfolding and self-assembly might be one of the crucial parameters for their different oncogenic effect. These studies thus call for the need of developing therapeutic strategies that consider the resultant mutant-variant as a target rather than mutation position. This is an important lead towards the understanding of cancer.