Host: The Japan Radiation Research Society
H2AXs surrounding the DSB region are phosphorylated at Ser139 to form γ-H2AX focus. Therefore, it is assumed that γ-H2AX foci are possible landmarks of DSB regions in the nucleus. However, many aspects about the mechanism of its phosphorylation has not still been elucidated.
In the present study, we compared the formation of γ-H2AX foci in three cell lines after some DSB evoking stimuli. Apparent γ-H2AX foci were formed in DU145 and BALB-3T3 after the irradiation of proton beams(200MeV, 0.5 - 1.0 Gy) and hyperthermia(44°C, 10min), whereas those in interphase HeLa cells were faint. H2AX in our HeLa cell does not seem to lack the capability of phosphorylation, since chromosomes in mitosis revealed apparent γ-H2AX foci after the irradiation of proton beams. Moreover, replication stall brought to HeLa cells by the administration of hydroxyurea caused strong fog-like H2AX phosphorylation in nuclei, as seen in other 2 cell lines.
These results suggest that at least 2 different mechanisms are involved in the phosphorylation of H2AX , and the major pathway in response to DSB formation is lost or diminished in our HeLa line at the interphase of the cell cycle. Relationship between H2AX and other factors concerning DSB detection and repair were further examined.
