Chromatin Immunoprecipitation (ChIP) Assay

The (chromatin immunoprecipitation) ChIP assay was performed, as previously described [31 (link)]. Cells were crosslinked with 1% formaldehyde for 30 min and then sonicated to shear the chromatin fragments. Sonicated chromatin was immunoprecipitated using an antibody overnight at 4 °C. The antibodies used for the ChIP assay were anti-Pol II (Millipore, Burlington, MA, USA), anti-p65 (Abcam, San Francisco, CA, USA), anti-MLL1 (Abgent, San Diego, CA, USA), and anti-H3K4me3 (Active motif, Carlsbad, CA, USA). After reverse crosslinking by heating, RT-qPCR was performed on the purified DNA fragment using a LightCycler^® 480 II system and SYBR Green I Master (Roche). The results are shown as the mean ± standard deviation (SD), expressed as a percentage of input chromatin. The primers used to amplify the HMOX1 promoter or enhancer region are listed in Supplementary Table S2.