Regulation and assembly of nuclear DNA repair centres

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Genetic defects in DNA repair genes are associated with increased cancer risk in humans. For example, BRCA1 and BRCA2 gene mutations are the most common causes of familial breast cancer, and MLH1 gene mutations are the most common cause of familial non-polyposis colorectal cancer. We have identified a novel human DNA repair protein termed ASCIZ that performs a similar function to BRCA1 and BRCA2 in that it regulates the concentration of the RAD51 repair protein in specific DNA repair centres in the cell nucleus. However, ASCIZ performs this function in response to different types of DNA damage than BRCA1-BRCA2, and it acts in concert with the MLH1 protein. Here we want to study how ASCIZ regulates the assembly of DNA repair centres, and if it does so with support by the BRCA1-BRCA2 proteins. We also want to know if DNA repair functions of the RAD51 protein are diminished when it is not located in repair centres, and we want to identify novel proteins involved in this process. Our preliminary data show that cells that lack ASCIZ become dramatically hypersensitive to DNA damaging agents that are similar to clinically used chemotherapy drugs. We hope that our studies may identify possible approaches to develop drugs against ASCIZ and related proteins in order to kill cancer cells more effectively.