Host: The Japan Radiation Research Society
Histone H2AX is rapidly phosphorylated by ATM and DNA-PKcs in response to DNA double-strand breaks induced by ionizing radiation and various cellular processes including V(D)J recombination, meiotic recombination and apoptosis. In addition, the H2AX phosphorylation takes place in S-phase cells subjected to UV irradiation or hydroxyurea treatment and seems to be mediated by ATR, which is recruited to single-stranded DNA regions (ssDNA) generated by replication arrest, with the aid of its partner ATRIP and ssDNA-binding protein RPA. We have recently found that UV-induced H2AX phosphorylation is also observed in G0-arrested human cells and that this phosphorylation depends on nucleotide excision repair (NER) as well as ATR. We proposed a model that NER process can be perturbed at a gap-filling step due to low levels of repair replication factors and the resultant ssDNA gap intermediates initiate the phosphorylation of histone H2AX (Matsumoto et al., J. Cell Sci. 120, 1104-1112, 2007). Here we show that the NER-dependent H2AX phosphorylation at G0 phase also occurs following treatment of chemical agents such as N-acetoxy-2-acetylaminofluorene and cisplatin, which generate DNA adducts reparable by NER. Furthermore, non-cycling peripheral T-lymphocytes isolated from wild-type mice exhibit H2AX phosphorylation following UV exposure, whereas those from NER-deficient mice do not, indicating this phosphorylation is again NER-dependent. In this workshop, we will further present our ongoing work and discuss on NER-dependent H2AX phosphorylation in vivo.
