title: Histone H2AX Is Involved in FoxO3a-Mediated Transcriptional Responses to Ionizing Radiation to Maintain Genome Stability.
abstract: Histone H2AX plays a crucial role in molecular and cellular responses to DNA damage and in the maintenance of genome stability. It is downstream of ataxia telangiectasia mutated (ATM) damage signaling pathway and there is an emerging role of the transcription factor FoxO3a, a regulator of a variety of other pathways, in activating this signaling. We asked whether H2AX may feedback to FoxO3a to affect respective FoxO3a-dependent pathways. We used a genetically matched pair of mouse embryonic fibroblast H2AX(+/+) and H2AX(-/-) cell lines to carry out comprehensive time-course and dose-response experiments and to show that the expression of several FoxO3a-regulated genes was altered in H2AX(-)(/-) compared to H2AX(+/+) cells at both basal and irradiated conditions. Hspa1b and Gadd45a were down-regulated four- to five-fold and Ddit3, Cdkn1a and Sod2 were up-regulated 2-3-fold in H2AX(-/-) cells. Using the luciferase reporter assay, we directly demonstrated that transcriptional activity of FoxoO3a was reduced in H2AX(-/-) cells. FoxO3a localization within the nuclear phospho-ATM (Ser1981) foci in irradiated cells was affected by the H2AX status, as well as its posttranslational modification (phospho-Thr32). These differences were associated with genomic instability and radiosensitivity in H2AX(-/-) cells. Finally, knockdown of H2AX in H2AX(+/+) cells resulted in FoxO3a-dependent gene expression patterns and increased radiosensitivity that partially mimicked those found in H2AX(-/-) cells. Taken together, our data suggest a role for FoxO3a in the maintenance of genome integrity in response to DNA damage that is mediated by H2AX via yet unknown mechanisms.
authors.affiliation: Canadian Nuclear Laboratories, Stn 51, Chalk River, ON K0J 1P0, Canada. stephane.tarrade@etu.unilim.fr.
authors.forename: Stephane
authors.initials: S
authors.lastname: Tarrade
authors.affiliation: Canadian Nuclear Laboratories, Stn 51, Chalk River, ON K0J 1P0, Canada. tanya_bhardwaj@live.com.
authors.forename: Tanya
authors.initials: T
authors.lastname: Bhardwaj
authors.affiliation: Canadian Nuclear Laboratories, Stn 51, Chalk River, ON K0J 1P0, Canada. matthew.flegal@cnl.ca.
authors.forename: Matthew
authors.initials: M
authors.lastname: Flegal
authors.affiliation: Canadian Nuclear Laboratories, Stn 51, Chalk River, ON K0J 1P0, Canada. lindsey.bertrand@cnl.ca.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Bertrand
authors.affiliation: Institute of Biology, Komi Science Center of RAS, 28b Kommunisticheskaya St, Syktyvkar 167982, Russia. vellio@yandex.ru.
authors.forename: Ilya
authors.initials: I
authors.lastname: Velegzhaninov
authors.affiliation: Institute of Biology, Komi Science Center of RAS, 28b Kommunisticheskaya St, Syktyvkar 167982, Russia. amoskalev@list.ru.|Department of Ecology, Syktyvkar State University, Syktyvkar 167001, Russia. amoskalev@list.ru.|Laboratory of Genetics of Aging and Longevity, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region 141700, Russia. amoskalev@list.ru.
authors.forename: Alexey
authors.initials: A
authors.lastname: Moskalev
authors.affiliation: Canadian Nuclear Laboratories, Stn 51, Chalk River, ON K0J 1P0, Canada. dmitry.klokov@cnl.ca.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Klokov
mesh_terms: D000818:Animals; D004307:Dose-Response Relationship, Radiation; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000528:radiation effects; D055785:Gene Knockdown Techniques; D042822:Genomic Instability / Q000528:radiation effects*; D006657:Histones / Q000172:deficiency / Q000378:metabolism*; D042541:Intracellular Space / Q000378:metabolism / Q000528:radiation effects; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects; D011836:Radiation Tolerance / Q000528:radiation effects; D011839:Radiation, Ionizing; D015203:Reproducibility of Results; D013997:Time Factors; D014158:Transcription, Genetic / Q000528:radiation effects*
chemical_list: D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006657:Histones; C474033:FoxO3 protein, mouse; C475961:gamma-H2AX protein, mouse
keywords: DNA damage signaling; FoxO3a; H2AX; genome stability; ionizing radiation; stress response