Identification of Naval Inhibitory Peptides of Protein-Protein Interactions Involved in DNA Repair as Potential Drugs in Breast Cancer Treatment

Abstract

Abstract : We have evaluated two strategies for identifying inhibitors of the DNA repair pathway. We used the yeast reverse two hybrid system to screen for inhibitory peptides of the Rad51 protein in order to disrupt the homologous recombination pathway from a plasmid library coding for 15 amino acid peptides. While we succeeded in generating a library of sufficient complexity, because of inherent technical issues involved we were not successful in identifying the inhibitory peptides. For identifying inhibitors of the Ku70/80 complex (the important component of the NHEJ pathway) we used structure-based virtual ligand screening using DOCK. We identified four compounds from the in-silico screen as also having biochemical activity in a Ku70/80 DNA binding assay. Two of the compounds effectively sensitized cancer cells to DNA damaging agents while having little toxicity themselves. Our results demonstrate the validity and importance of both our target (DNA repair) as well as the approach we used to identify inhibitors of the target (DOCK). Targeting the DNA repair pathway is effective in sensitizing cells to DNA damaging agents such as topoisomerase inhibitors and ionizing radiation. Structure-based drug screening using virtual libraries may be a useful and economical way to identify inhibitors of large multi subunit complexes.