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    Home > Research & Grants > Grants Program > Research Grants > Research Grants Awarded > Abstract
    Awarded Grants
    Structure and Biochemistry of the Homologous DNA Recombinase Rad51

    Scientific Abstract:
    Homologous recombination is critical for maintaining genomic stability. In eukaryotes its major role is accurate repair of DNA double strand breaks which occur in response to a variety of damaging agents. The central recombinase in this repair pathway is Rad51. Two of the proteins that directly interact with Rad51 are the products of breast cancer predisposing genes BRCA1 and BRCA2. The major objective of the proposed research is to understand the structural mechanisms governing Rad51 activation and function. An interdisciplinary approach will be taken by combining structural studies with biochemical investigations. Besides directly contributing to a better understanding of the eukaryotic homologous recombination repair mechanisms this study could also find important applications in cancer therapy. Mutations in proteins that control Rad51 recruitment and/or activation have been associated with a variety of human cancers. There is increasing evidence (reviewed by Henning & Sturzbecher, 2003) that the level of Rad51 activity in tumor cells that contain such mutations is directly correlated to resistance of tumors to therapeutic drugs and radiation therapy. Structural models that permit a detailed understanding of Rad51 activation and function might therefore prove useful in the design of drugs which can modulate Rad51 activity and improve the efficacies of radiation therapy and chemotherapy. The active form of Rad51 is an extended helical filament that coats DNA substrates and carries out the homology search and strand exchange reactions. Based on a preliminary structure of a Rad51 filament, the idea that structural changes that couple DNA binding with ATP binding and/or hydrolysis control the activity of the Rad51 recombinase provides a conceptual framework for this study. The research proposed has the following objectives: 1) To reveal how the DNA substrates are bound and displayed within the Rad51 filament in order to delineate the structural bases for homology recognition and strand exchange reactions, 2) To test the validity and functional importance of the protein-protein interface that appears to be characteristic to the active form of the Rad51 filament and 3) By combining information from 1) and 2) with structural data on the inactive form of Rad51 protein to unravel the intrinsic structural mechanism governing Rad51 activation. To accomplish these goals X-ray crystallography and molecular modeling will be employed in combination with site directed mutagenesis and biochemical studies.

    Lay Abstract:
    DNA double strand breaks occur in response to a variety of external agents such as ionizing radiation, toxins, etc. They are considered the most dangerous type of DNA damage. In eukaryotes the major pathway responsible for efficiently and accurately repairing DNA double strand breaks is homologous recombination repair (HRR). The central recombinase in this pathway, Rad51- a protein highly conserved among eukaryotes-carries out the search for homology and strand pairing reactions. The major objective of the proposed research is to understand the structural mechanisms governing Rad51 activation and function. An interdisciplinary approach will be taken by combining structural studies with biochemical investigations. Besides directly contributing to a better understanding of the eukaryotic homologous recombination repair mechanisms this study could also find important applications in cancer therapy. Two of the proteins that directly interact with Rad51 are the products of breast cancer predisposing genes BRCA1 and BRCA2. There is increasing evidence (reviewed by Henning & Sturzbecher, 2003) that the level of Rad51 activity in tumor cells that contain cancer-predisposing mutations is directly correlated to resistance of tumors to therapeutic drugs and radiation therapy. Structural models that permit a detailed understanding of Rad51 activation and function might therefore prove useful in the design of drugs which can modulate Rad51 activity and improve the efficacies of radiation therapy and chemotherapy.