IRF8 suppresses PU.1 expression. (A) IRF8 is present at the promoter region of PU.1 in vivo. ChIP analyses were performed with NFS-202 cells or purified spleen B cells. Protein-DNA complexes were immunoprecipitated by addition of antibody to IRF8 and analyzed by PCR for the presence of PU.1 promoter sequences. (B) qPCR analysis of IRF8 and PU.1 expression in cells expressing a repressive IRF8 siRNA. IRF8 Nos. 2 and 5 are 2 clones from IRF8 siRNA–treated cells. (C) Western blotting analysis of IRF8 and PU.1 expression in IRF8 siRNA–expressing cells. (D) Western blotting analysis of IRF8 and PU.1 expression in NFS-203 cells expressing pCDNA-Irf8 or an empty pCDNA vector as indicated. The numbers are arbitrary units of protein intensities normalized by β-actin. All data are representative of 2 to 4 independent experiments.