THE FUNCTION OF RECQ HELICASE GENE FAMILY IN DNA RECOMBINATION AND JOINING

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Bloom syndrome and ataxia-telangiectasia are autosomal recessive human disorders characterized by immunodeficiency, genome instability and predisposition to develop cancer. Recent data reveal that the products of these two genes, BLM and ATM, interact and function together in recognizing abnormal DNA structures. To investigate the function of these two molecules in DNA damage, recognition, we generated double knockouts of ATM-/-BLM-/-In the DT40 chicken B-lymphocyte cell line. The double mutant cells were viable and exhibited a variety of characteristics of both ATM-/-and BLM-/-cells. There was no evidence for exacerbation of either phenotypes ; however, the more extreme radiosensitivity seen in ATM-/-and elevated sister chromatid exchange seen in BLM-/-cells were retained in the double mutants. These results suggest that ATM and BLM have largely distinct roles in recognizing different forms of damage in DNA, but also compatible with partially overlapping functions in recognizing breaks in radiation-damaged DNA.In addition, we showed that the combinational analysis of immunoblotting and immunohistochemistry is a useful approach to screening of BS.