FIGURE 1.

Reduction of endogenous Fli-I attenuated the expression of ER target genes. A, domains of Fli-I. GelA and GelB, the gelsolin-like domain consisting of two large tandem repeats. The six numbered regions represent small repeated modules homologous to the actin binding motifs of gelsolin. B, depletion of Fli-I mRNA and protein by siRNA transfection. MCF7 cells were transfected with siRNA specific for Fli-I (siFli-I) or siNS and grown in hormone-free media for 72 h. Total RNA was analyzed for Fli-I mRNA by qRT-PCR and normalized to the level of GAPDH mRNA. Protein levels of Fli-I, ER, and β-actin were assessed by immunoblot. C, effect of reduced Fli-I on expression of estrogen-responsive genes. MCF7 cells were transfected with siFli-I or siNS and grown in hormone free-media. After 72 h cells were treated with 100 nm E2 or vehicle for 24 h. Total RNA was analyzed by qRT-PCR. The levels of pS2, GREB1, and cathepsin D mRNAs were normalized to that of GAPDH mRNA. Results shown in the bar graphs are the means and S.D. of data from seven independent experiments. p values were determined by paired, two-tailed t tests from the seven independent experiments, as indicated by the brackets in the figures. Results of all seven independent experiments are shown in supplemental Table S1. The line graph shows the correlation between reduction of Fli-I and pS2 mRNA levels. From the seven independent experiments in supplemental Table S1, % reduction of pS2 mRNA was plotted against % reduction of Fli-I mRNA, and the R² value was calculated.