Estrogen changes c-Myb activity. (A) MCF-7 cells were deprived of estrogen for 48 hr then stimulated with 10 nM 17-beta-estradiol for 6, 12 or 24 hours. QPCR was used to measure the levels of CCNB1, CXCR4, JUN, KLF4 and EPB41 RNAs. Error bars show standard deviation in triplicate PCR reactions, and results are relative to the estrogen-deprived cells. (B) MCF-7 cells were transduced with retroviral vectors expressing doxycycline inducible shRNAs (scrambled or c-myb specific). Each cell line was induced for 24 hr with doxycycline and the relative expression of c-myb, CCNB1, CXCR4, JUN, KLF4 and EPB41 RNAs was measured by QPCR. Data are normalized to the scrambled control shRNA.