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Abstract
Grant Number: 1R03MH084119-01 Project Title: A Screen for Modulators of Human Rad51, a Key DNA Repair Protein
PI Information: Name Title MAZIN, ALEXANDER V. amazin@drexelmed.edu Abstract: DESCRIPTION (provided by applicant): Ionizing radiation (IR) and inter-strand cross-linking agents (ICL) induce DNA double-stranded breaks (DSB). DSB are the most harmful type of DNA damage, which cause genome instability, cancer, genetic diseases, and premature aging. The system of homologous recombination (HR) is responsible for the repair of DSB repair in humans. However, DSB-inducing agents, IR and ICL, are also used in anti-cancer therapy. In order to increase the efficiency of this therapy, we propose to suppress HR in cancer cells by using specific inhibitors against a key human HR protein, Rad51 (hRad51). These inhibitors will help to develop novel combination therapies that allow to reduce doses of IR and ICL thereby decreasing their cytotoxicity. Specific inhibitors and stimulators of hRad51 will also present a valuable tool in fundamental studies on the mechanisms of HR in human cells. Therefore, the Aim of this proposal is to identify specific inhibitors and stimulators of hRad51 using high throughput screening (HTS) of the molecular libraries of reagents. hRad51 possesses a unique activity, it promotes DNA strand exchange between homologous DNA molecules, a basic step of HR. We have developed a fluorimetric assay that allows to measure DNA strand exchange activity of hRad51 in vitro. We will use this assay for the primary HTS. The selected compounds will be validated using conventional radioactively-based DNA strand exchange assays (secondary screen).Using microbial hRad51 homologues and structurally unrelated hRad54 protein we will determine the selectivity and specificity of the selected compounds. In continuation of this grant, we will employ the selected compounds for analysis of the mechanisms of HR in humans. The therapeutic potential the prioritized compounds will be examined using reconstituted HR system in vitro, transformed human cells, and immuno-deficient mice with transplanted human xenografts (SCID-hu mice).
Public Health Relevance: NARRATIVE OF THE PROJECT In humans, the system of homologous recombination performs crucial functions including DNA repair, segregation of homologous chromosomes, propagation of genetic diversity, and maintenance of telomeres. In cancer cells homologous recombination is responsible for the repair of DNA double-strand breaks induced by ionizing radiation and cross-linking agents, which are used in tumor therapy. We propose to perform a high throughput screen for specific inhibitors of hRad51, a key HR protein, which can be used for investigation of the mechanisms of homologous recombination and help to develop more efficient anti-cancer therapies.
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Institution: DREXEL UNIVERSITY OFFICE OF RESEARCH PHILADELPHIA, PA 19104 Fiscal Year: 2008 Department: BIOCHEMISTRY AND MOLECULAR BIOLOGY Project Start: 01-JUN-2008 Project End: 31-MAY-2009 ICD: NATIONAL INSTITUTE OF MENTAL HEALTH IRG: ZMH1