The most common cause of protein loss of function is the destabilization of its native structure, hence the decrease of its thermodynamic stability. Experimental studies on thermodynamic stability of some natural missense protein variants expressed in cancer tissues reveal a decrease in thermal stability and an increase of protein flexibility. The expression of these single residue variants (SRVs) is caused by non synonymous single nucleotide polymorphisms (nsSNPs) that occurr in the DNA coding region and encode a change in the amino acid sequence. The single amino acid substitution can potentially affect the protein structure-function relationships in different ways, such as changes in protein function, stability, flexibility and interaction with other proteins, nucleic acids, and other molecules. Several investigations have addressed the effect of SRV on protein stability, functions and interactions. The stability of the SRVs has been considered to be responsible of the impact of the mutation on the pathological conditions or on the genetic susceptibility to diseases. The aim of this project is the study of some natural SRVs of human frataxin (hFXN), an iron binding protein involved in iron-sulfur cluster assembly. In this study we will select some natural SRV, of hFXN that are expressed in cancer tissues and reported in COSMIC database. These variants will be characterized to investigate the effect of single amino acid substitution on hFXN thermal and thermodynamic stability and structure in solution.
In the post-genomic era, how human genetic and somatic variations are associated with diseases and how mechanisms form the basis of the relationship between genotype and phenotype are still open questions. Available data on polymorphisms in the human genome are expanding rapidly, though, knowledge of the molecular mechanisms of many genetic diseases is lagging, due to the laborious and time consuming nature of experimental studies. Experimental analysis of the impact of nonsynonymous single nucleotide polymorphisms (nsSNPs) on protein structure, function and stability studies require mutagenesis, protein expression and purification followed by thermal and chemical unfolding: the entire process is therefore costly and time consuming. Biophysical and stability of protein variants help when analyzing the effect of variations on protein structure and function, however, information is available for only few proteins. There is need to solve the 3D structure of natural variant to explore, at the atomic level, the consequences of the amino acid substitution derived from single nucleotide polymorphism [1]. Structural analysis of nsSNPs in the human DNA sequences may also help to predict personal response to certain drugs, susceptibility to environmental factors, and risk of developing particular diseases.
The aim of this project is the study of single residue variants, expressed in cancer tissues, of hFXN, an iron binding protein involved in iron-sulfur cluster assembly in mitochondria. Cancer cells are able to adapt to survive in difficult conditions, like for example in O2 deficiency, through a reprogramming of their metabolism according to their requirements [2]. In the general reprogramming of the metabolism, mitochondria play a central role in the production of energy and metabolic intermediates to be utilized for the increased biosynthetic demand of proliferating tumor cells [3].
A detailed understanding of the changes of the investigated gene products at the molecular level to assess how genetic variations impact the protein folding, structure, function and interactions is required to develop new therapeutic strategies, particularly in the search of small molecules able to selectively interact with the variants, which is an essential preliminary step to personalized medicine, and help to identify new potential therapeutic targets. Precision medicine aims at classifying individuals into subpopulations that differ in their susceptibility to a particular disease, in the biology and/or prognosis of those diseases they may develop, or in their response to a specific treatment. The structural analysis of protein variants expressed in cancer tissues may help in understanding the molecular basis of the disease and, since individuals carrying variants may respond differently to drugs, it may provide information for personalized drugs tailored to the individual variant.
References
1. Bhattacharya, R et al., PLoS One 12 2017; e0171355
2. Bertout JA et al., Nat Rev Cancer. 2008;8: 967¿975
3. Torti SV et al., Cancer Res. 2011; 71:1511-1514