Changes to wild-type p53 that make it partially or completely lose or alter its function, to enable the progression of tumors, occur in ~ 50% cancers, highlighting the role of p53 as a significant tumor suppressor. Usually p53 is inactivated through the mutation of the gene in somatic cells and at times, through the disruption of pathways that are vital for p53 activation. Because of the prevalence of loss-of-p53 in most cancers, interventions to target the reactivation of defective p53 pathways are in progress. Since peptides are easier to synthesize, administer and are safer than most cancer drugs in the market, there is an interest in considering peptide derivatives in drug design. By synthesizing a small peptide from the C-terminal domain of p53 we tested if p53 would interact with this small peptide. This interaction is significant since the C-terminal domain of p53 is involved in the self-activation of p53 and the goal of peptide therapy in this case would be to restore p53 self-activation. The peptide was synthesized by solid-phase peptide synthesis and its affinity for p53 was tested using microarray printing technology. Based on the results, the C1 peptide, a small peptide with 15 amino acids, binds to p53. Our findings suggest that C1 should be investigated further, in order to develop it as an anti-cancer drug.
The ETS family of transcription factors is made up of 30 evolutionarily-related proteins that are characterized by the DNA-binding ETS domain, which is highly conserved throughout the family. All ETS proteins bind to a consensus 5’-GGA(A/T)-3’ DNA sequence motif, yet regulate transcription at a diverse array of genomic targets, so the mechanisms of their regulation are of particular interest. The members of the ETV1/4/5 subfamily are aberrantly expressed in multiple cancers, and display a biochemical phenomenon called autoinhibition in which intramolecular interactions decrease the affinity with which the protein binds to DNA. This project quantitatively maps the autoinhibition of ETV5, and establishes relationships between autoinhibitory structural elements and corresponding effects on DNA affinity. I show that ETV5 contains autoinhibitory sequences both N- and C-terminal to the ETS domain. Additionally, I demonstrate that both helices and unstructured regions C-terminal to the ETS domain play a role in autoinhibition. Finally, I establish that a single residue, Met457, plays a role in mediating autoinhibition in three separate C-terminal truncations.
Dr. Ajit Singh, president of the Oncology Care Systems Group of Siemens Medical Solutions, explains new advances in the war against cancer, and how new technologies are shattering old conceptions of how to treat it. Singh is an expert in the future of radiation oncology and the role of information technology in today's managed health care environments.