Cell cycle dependent phosphorylation and focus-formation of histone H2AX in X-irradiated malignant B-lymphocyte cell lines : detection and repair of ionizing radiation induced DNA double strand breaks

Abstract

Production of DNA damage is the basis of cancer treatments, such as radiotherapy. The limitation of the treatment dose tends to be how well the tumor and normal cell within the body can tolerate the therapy. In order to improve the effectiveness of treatments, it is important to understand how cells respond to and repair ionizing radiation (IR)induced DNA damage. Of particular importance is the measurement of repair of IR-induced DNA DNA double-strand breaks (DSBs), because these lesions, if unrepaired, lead to cell death. Recently it has been shown that histone H2AX becomes phosphorylated (termed gamma-H2AX) immediately after ionizing radiation treatment and is believed to recruit DNA repair factors to sites of the DNA DSBs .In association with DSB repair, it has been reasoned that the kinetics of formation and loss of gamma-H2AX foci may be related to the efficiency of the DNA breaks repair.Although image analysis of gamma-H2AX foci containing thousands of gamma-H2AX molecules are found at each DSB, making it possible to detect a single break within a nuclease.The main purpose of this project was to determine the cell cycle specific phosphorylation and focus formation of gamma-H2AX after IR treatment of cancer cells. We also wanted to assess the role of the tumor suppressor TP53 in gamma-H2AX induction, as well as in the repair, presumably reflected in the disappearance of gamma-H2AX. Another question was whether repair is connected to cell cycle arrest and apoptosis.