Pathways of DNA double strand break repair in mammalian cells

DNA-dependent protein kinase (DNA-PK) has recently been shown to be involved in pathway of double strand break repair mammalian cells, which operates primarily in the Gl phase of the cell cycle. Recent evidence suggests that this is a process involving non-homologous end rejoining. Yeast cells, in contrasts, rejoin the majority of their breaks by a RAD52 dependent mechanism involving homologous recombination. Recently yeast cells have also been shown to possess a Ku dependent mechanism of break rejoining, which plays only a minor role in repairing radiation induced double strand breaks. Studies on the mammalian DNA-PK defective mutants suggests that a second mechanism of double strand break rejoining also exists in mammalian cells, for which homologous recombination is a likely candidate. (author)