a, Immunoblot analysis of ATM from colon epithelial cells. Densitometric quantification of signal intensity normalized to loading controls (n = 3; mean ± s.e.m.; P = 0.004). b, Schematic representation of STAT3-binding sites in the Atm gene locus. c, STAT3 ChIP was performed to determine specific pulldown at the transcription factor-binding sites (start, mid, end) in the promoter regions of the Atm gene and at a control site within the Atm gene (cold). Genomic DNA from colon epithelial cells of Il22+/+ and Il22−/− mice before and after in vivo stimulation with recombinant IL-22. Results represent specific pulldown relative to a DNA input sample (start, n = 14; mid, n = 7; end, n = 12; cold, n = 8; mean ± s.e.m.). d, e, Mice of the indicated genotypes were irradiated with 8 Gy. d, Immunofluorescence analysis for γH2AX (red) and EpCam (blue) in the entire colon was performed 8 h after irradiation. Scale bars, 500 µm. e, Quantification (control, 4 h and 24 h, n = 2; 8h, n = 3; mean ± s.e.m.) of γH2AX+ nuclei per colon before and at the indicated time points after irradiation. f, Immunoblot analysis of H2AX protein and densitometric quantification of signal intensity (normalized to loading controls) in primary colon epithelial cells of Il22+/+ and Il22−/− mice (mean ± s.e.m.; n = 2). g, h, Mice were irradiated with 8 Gy or injected intraperitoneally with AOM. Immunofluorescence analysis of colon sections was performed 8 h after damage. Quantification (g; n = 3, mean ± s.e.m.) of γH2AX+EpCam+cells and representative immunofluorescence images (h) after γH2AX (red) and EpCam (blue) staining. Scale bars, 25 µm.