PRMT1 and dimethyl H4R3 are targeted to the β-globin locus by transcription factor USF1. (A) Cross-linked chromatin prepared from MEL cells was immunoprecipitated with α-USF1 antibody, and USF1-DNA complexes from the first ChIP were subjected to a second ChIP using α-PRMT1 antibody. The protein/DNA complexes were reversed and the purified DNA fragments were amplified using primers specific for the HS2 core, ϵ^y-globin promoter and β^major-globin promoter. (B) MEL cells were cultured in the presence or absence of 1.5% DMSO. The cross-linked chromatin was analyzed by ChIP assay using antibodies specific to dimethyl H4R3. The protein/DNA complexes were then reversed and the purified DNA fragments were amplified using primers specific for HS2 and β^maj-globin promoter. (C) ES cells were cultured in the presence or absence of 2 U/mL EPO. The cross-linked chromatin was analyzed by ChIP assay using antibodies specific for USF1 (top), PRMT1 (middle), and dimethyl H4R3 (bottom). The MyoD promoter and the p45 promoter were also analyzed as inactive and active promoter controls, respectively. Significant difference by Student t test: *P < .05, **P < .01. Shown are the mean ± SDM of 3 independent experiments.