title: Nuclear localization of mouse Ku70 in interphase cells and focus formation of mouse Ku70 at DNA damage sites immediately after irradiation.
abstract: To elucidate the mechanisms of DNA repair pathway is critical for developing next-generation radiotherapies and chemotherapeutic drugs for cancer. Ionizing radiation and many chemotherapeutic drugs kill tumor cells mainly by inducing DNA double-strand breaks (DSBs). The classical nonhomologous DNA-end joining (NHEJ) (C-NHEJ) pathway repairs a predominant fraction of DSBs in mammalian cells. The C-NHEJ pathway appears to start with the binding of Ku (heterodimer of Ku70 and Ku80) to DNA break ends. Therefore, recruitment of Ku to DSB sites might play a critical role in regulating NHEJ activity. Indeed, human Ku70 and Ku80 localize in the nuclei and accumulate at microirradiated DSB sites. However, the localization and regulation mechanisms of Ku70 and Ku80 homologues in animal models, such as mice and other species, have not been elucidated in detail, particularly in cells immediately after microirradiation. Here, we show that EYFP-tagged mouse Ku70 localizes in the interphase nuclei of mouse fibroblasts and epithelial cells. Furthermore, our findings indicate that EYFP-mouse Ku70 accumulates with its heterodimeric partner Ku80 immediately at laser-microirradiated DSB sites. We also confirmed that the structure of Ku70 nuclear localization signal (NLS) is highly conserved among various rodent species, such as the mouse, rat, degu and ground squirrel, supporting the idea that NLS is important for the regulation of rodent Ku70 function. Collectively, these results suggest that the mechanisms of regulating the localization and accumulation of Ku70 at DSBs might be well conserved between the mouse and human species.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Koike
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Yutoku
authors.forename: Aki
authors.initials: A
authors.lastname: Koike
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000502:physiology / Q000528:radiation effects*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism* / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects*; D059766:DNA End-Joining Repair / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000502:physiology / Q000528:radiation effects*; D005455:Fluorescent Antibody Technique; D007399:Interphase / Q000528:radiation effects*; D000072200:Ku Autoantigen; D051379:Mice
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; C000606511:Xrcc6 protein, rat; D000072200:Ku Autoantigen