Analysis of XRCC4 gene function in nonhomologous end joining

Abstract

Nonhomologous DNA end joining (NHEJ) is the major pathway for repairing DNA double-strand breaks (DSBs) in mammalian cells. The non-homologous end-joining pathway is required both for normal development and for suppression of tumors. In the non-homologous end joining pathway of DNA double-strand break repair, the ligation step is catalysed by a complex of XRCC4 and DNA ligase IV. To address the role of XRCC4 in human cells, we have used gene targeting human HCT116 colon cancer cells to functionally inactivate the XRCC4 locus. The homolozygously null XRCC4 cells showed a growth defects and hypersensitivity to ionizing radiation. To analyze functions of XRCC4, we attempted to introduce XRCC4 cDNA tagged with FLAG into the XRCC4 (-/-) cells. The clones transfected with the XRCC4 cDNA showed a partial correction of ionizing radiation sensitivity. Further analysis is in progress.