Down-regulation of c-Myc expression in ICSBP-transduced cells. (A) Semiquantitative RT-PCR analysis for c-Myc transcripts. (B) Wright-Giemsa stain of Tot2p210 cells transduced with retroviruses carrying hormone-binding domain of estrogen receptor (ER) or ICSBP/ER chimeric construct. Cells were either left untreated or treated with 1 μM β-estradiol (Est) for 24 hours (original magnification × 600). (C) RNA blot analysis for the c-Myc transcripts. Tot2p210 cells transduced with indicated viruses were treated with 1 μM β-estradiol. Total RNA (5 μg) from cells treated for the lengths of time was analyzed. The bottom panel indicates 28S ribosomal RNA. (D) Effect of cycloheximide (CHX) on ICSBP/ER-mediated repression of c-Myc expression. The top panel indicates RNA blot analysis; the bottom panel, quantification of the c-Myc transcripts. CHX (10 μg/mL) was added 10 minutes before addition of estradiol. The expression level in CHX + Est samples was normalized by the values in CHX alone-treated cells.