The nuclear aryl hydocarbon receptor is involved in regulation of DNA repair and cell survival following treatment with ionizing radiation

• Published in: Toxicology letters 2016-01, Vol.240 (1), p.122-129
• Main Authors: Dittmann, K.H., Rothmund, M.C., Paasch, A., Mayer, C., Fehrenbacher, B., Schaller, M., Frauenstein, K., Fritsche, E., Haarmann-Stemmann, T., Braeuning, A., Rodemann, H.P.
• Format: Article
• Language: English
• Subjects: Acetylation; Activation; AhR; Animals; Aromatic compounds; Cell Line, Tumor; Cell Survival - radiation effects; CHO Cells; Cricetulus; Deoxyribonucleic acid; DNA repair; DNA Repair - radiation effects; DNA-Activated Protein Kinase - genetics; DNA-Activated Protein Kinase - metabolism; DNA-PK; Gamma Rays; Gene Expression Regulation; Hep G2 Cells; Histone modification; Histones; Histones - genetics; Histones - metabolism; Humans; Ionizing radiation; Lamin Type A - genetics; Lamin Type A - metabolism; Lipid Peroxidation - radiation effects; Microscopy, Confocal; Proteins; Receptors; Receptors, Aryl Hydrocarbon - genetics; Receptors, Aryl Hydrocarbon - metabolism; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Cytoplasmic and Nuclear - metabolism; Repair; Transcriptional Activation; γ-H2AX
• ISSN: 0378-4274; 1879-3169
• DOI: 10.1016/j.toxlet.2015.10.017

•Ionizing radiation induces nuclear translocation of AhR.•AhR knockdown hampers formation of γ-H2AX foci.•Nuclear AhR is needed for ATM activation and chromatin relaxation.•AhR knockdown is associated with radio-sensitization. In the present study, we explored the role of the aryl hydrocarbon receptor (AhR) for γ-H2AX associated DNA repair in response to treatment with ionizing radiation. Ionizing radiation was able to stabilize AhR protein and to induce a nuclear translocation in a similar way as described for exposure to aromatic hydrocarbons. A comparable AhR protein stabilization was obtained by treatment with hydroxyl-nonenal—generated by radiation-induced lipid peroxidation. AhR knockdown resulted in significant radio-sensitization of both A549- and HaCaT cells. Under these conditions an increased amount of residual γ-H2AX foci and a delayed decline of γ-H2AX foci was observed. Knockdown of the co-activator ARNT, which is essential for transcriptional activation of AhR target genes, reduced AhR-dependent CYP1A expression in response to irradiation, but was without effect on the amount of residual γ-H2AX foci. Nuclear AhR was found in complex with γ-H2AX, DNA-PK, ATM and Lamin A. AhR and γ-H2AX form together nuclear foci, which disappear during DNA repair. Presence of nuclear AhR protein is associated with ATM activation and chromatin relaxation indicated by acetylation of histone H3. Taken together, we could show, that beyond the function as a transcription factor the nuclear AhR is involved in the regulation of DNA repair. Reduction of nuclear AhR inhibits DNA-double stand repair and radiosensitizes cells. First hints for its molecular mechanism suggest a role during ATM activation and chromatin relaxation, both essential for DNA repair.