Recombinant il 22

Monoclonal anti-IL-22 (Clone 8E11) blocking antibody was kindly provided by Genentech (South San Francisco, USA). Anti-IL-22 (150μg/mouse) or control IgG were injected 36h, 12h before and 12h after inducing DNA damage. For reconstitution, mice were injected with recombinant IL-22 (400ng/mouse, Peprotech) i.p. every 8h for three days prior to the damage induction and at 8h and 16h afterwards. Epithelial cells were isolated 24h after damage. For the stimulation of ATM expression, mice were injected with recombinant IL-22 (500 ng/mouse, Peprotech) i.p. 12h and 2h prior to epithelial isolation.

Mice were injected 1 μg recombinant IL-22 (Peprotech) or PBS i.p. 1h prior to epithelial cell isolation. Epithelial cells were isolated as described above. Cells were resuspended in PBS and fixed with 0.75% paraformaldehyde. Fixation was stopped with glycine and cells were washed and lysed in 50mM Tris, 2.5mM EDTA, 0.1% NP-40 and 10 % Glycerol. Nuclei were lysed in 50mM Tris, 5mM EDTA and 0.25% SDS and subsequently sonicated in a Bioruptor Plus (Diagenode). Lysates were cleared by centrifugation and stored at -80°C. Protein-A-coated magnetic beads (Diagenode) were blocked with yeast tRNA (Life Technologies) and BSA (New England Biolab). Nuclear lysates were split in 10% input and 90% immunoprecipitation solutions. The latter was incubated with α-STAT3 (C-20; Santa Cruz Biotechnology) overnight rotating at 4°C. Protein-A coded magnetic beads were added and incubated for another 30min rotating at 4°C. Beads were purified and washed repeatedly. Bound DNA was eluted in 10mM TRIS, 1 mM EDTA and 2% SDS at 37°C for 15min. De-crosslinking was performed overnight at 65°C. RNA was removed by 1h incubation with RNAse A (Peqlab) at 37°C, followed by 1h incubation with Proteinase K (Peqlab) at 42°C. DNA was purified using PCR Purification Kit (Qiagen) according to the manufacturer’s instructions. All antibodies used are listed in Supplementary Information Table 2.