The Ino80 chromatin remodeling complex plays an important role in the repair ofradiation-induced DNA double strand breaks in lower eukaryotes. This discoveryprovides the first strong evidence that accessibility to DNA in the context of highlycompact chromatin structure is a critical factor in DNA damage response. It becomesincreasingly clear that maintenance of genome stability depends on highly coordinatedactions of DNA damage repair, cell cycle checkpoint, and chromatin remodelingmechanisms. While the first two mechanisms have been the subject of extensiveinvestigations during the past decades, the role of chromatin modification andremodeling in DNA damage response remains largely unclear, particularly in mammaliansystems. Our proposed studies are aimed at delineating how chromatin remodelingactivities support removal of DNA lesions and initiation of damage-induced cell cyclecheckpoint signals. Our focus will be on two key subunits of the Ino80 ATP-dependentchromatin remodeling complex, Ino80 and Arp5. Ino80 is a unique member of the SNF2superfamily that is believed to be a specialized chromatin remodeler assisting in DNArepair. Arp5 is an actin-related nuclear protein and an integral subunit of the Ino80complex. Mutations of either gene in budding yeast render cells hypersensitive to abroad spectrum of genotoxic agents. In this application, we seek to understand howIno80 modulates DNA damage responses. We have successfully created, viahomologous targeting, loss-of-function human cellular models for INO80 and ARP5.These genetic model systems will serve as unique tools to study the function of Ino80and Arp5 in cell proliferation, repair of ionizing radiation and UV-induced DNA lesions,damage-induced cell cycle arrest, and apoptosis. Our results are expected to furtherelucidate the mechanisms of the DNA damage response system and the molecularbasis of genomic instability at large. Our results should also be useful for identification ofnovel therapeutic targets, especially targets for radiation sensitization. NARRATIVEAccess to DNA lesions is a key prerequisite for many cellular mechanisms that act toprotect the integrity of the human genome. Studies proposed in this application seek tounderstand the role of chromatin remodeling complex in creating such access by usingmolecular and genetics approaches. Results from the proposed work have the potentialto unveil novel mechanism of genetic instability and to identify novel targets for cancertherapy.
Showing the most recent 10 out of 16 publications
