ChIP and Re-ChIP of KMT2B, ER, and H3K4me1

The ChIP and Re-ChIP assays were performed as described previously [24 (link)]. Briefly, Cell lysates were prepared, sonicated, and immunoprecipitated with anti-KMT2B (ab104444; abcam), anti-ERα (HC-20X; Santa Cruz Biotechnology, Inc), anti-RNA Pol II (05-623B; Millipore) or anti-H3K4me1 (07–436; Millipore) antibodies. The protein-DNA cross-linking of the immunoprecipitated complexes were reversed and the DNA was extracted for subsequent Real-Time qPCR analysis. The primer sets for the qPCR are listed in S2 Table. For the Re-ChIP experiments, after the initial ChIP with the first antibody, the protein-DNA complexes were eluted by incubation for 30 min at 37°C in 25 μl 10 mM DTT. After centrifugation, the supernatant was diluted 20 times with Re-ChIP buffer and subjected again to the ChIP procedure with the second antibody.