Competitive regulation of cytoprotective genes by p45 and Nrf2. (A) ChIP assays were performed with primary megakaryocytes derived from WT fetal livers using anti-p45 and anti–trimethyl-histone H3 (Lys4) antibodies. (B-C) ChIP assays were performed with primary megakaryocytes derived from p45-null and control fetal livers using anti-p45 and anti-Nrf2 antibodies (B) and anti–trimethyl-histone H3K4, anti–dimethyl-histone H3K4, anti–acetyl-histone H3, and anti–acetyl-histone H4 antibodies (C). Enrichment of the promoter regions containing MAREs of the Txas and Nqo1 genes is shown. The third intron of the Txas gene was used as a negative control. Quantitative analysis was performed, and the average values and SD were calculated from the triplicate samples (B-C). The Student t test was used to calculate statistical significance. *P < .02; **P < .002 (B-C). (D-E) Effect of p45 deletion on the expression of platelet genes (D) and cytoprotective genes (E) in the presence (top panels) and in the absence (bottom panels) of Nrf2. Quantitative RT-PCR was performed, and the relative values were calculated against the values of WT (D top panel), Nrf2^−/− (D bottom panel), the mixture of WT and p45^+/− (E top panel), and the mixture of Nrf2^−/− and Nrf2^−/−:p45^+/− (E bottom panel) megakaryocytes. The Student t test was used to calculate statistical significance. *P < .002; **P < .05; ***P < .1 (D-E).