Exploiting Synthetic Lethal Relationships: Chemical Inhibition of Recombinational Repair as a Strategy to Selectively Target Tumor Cells

摘要

Homologous recombination is a key cellular pathway to repair or tolerate complex DNA damage such as DNA double-stranded breaks, interstrand DNA crosslinks, or single-stranded DNA gaps. In addition, homologous recombination is required for the recovery of stalled or broken replication forks. The significance of these functions is highlighted by the use of physical (ionizing radiation) and chemical (topoisomerases inhibitors, interstrand crosslinkers) agents as principal modalities in anti-tumor therapy. The importance of the homologous recombination pathway for breast cancer is underlined by the critical function of the breast cancer tumor suppressor protein BRCA2 in RAD51 filament assembly, a central step in recombination. The objective of the research is to isolate small molecule inhibitors of homologous recombination to allow selective ablation of this pathway. Specifically, we are performing high throughput screens for two target proteins: the double-stranded DNA motor protein RAD54 and the DNA structure-selective endonuclease MUS81-EME1. We have completed a small molecule inhibitor screen for human RAD54 and are currently testing the specificity and in vivo effects of the lead candidates. For MUS81- EME1, we have designed and validated a fluorescence resonance energy transfer assay for the MUS81-EME1 nuclease and established the feasibility of this assay in FRET and QUENCH modes.