Figure 5.

The N terminus of SMRT is dispensable for synergistic coactivation of ERα by SRC-3 and SMRT. A, Schematic representation of SMRTτ and SMRT_short illustrating repression domains (black box) and CoRNR box motifs (striped box). The 47-amino-acid splice deletion in the C-terminal region of both SMRTτ and SMRT_short adjacent to ID1 is represented as a single horizontal line. The arrow indicates the location of the sequence targeted by this SMRT siRNA (Sαβ²). B, Representative Western blot analysis of SMRT (top) or actin (bottom) expression in cells obtained from HeLa cells transfected in parallel. C, HeLa cells were transfected with negative control (−) siRNA or the Sαβ² (+) siRNA directed against SMRT before transfection with vectors for ERα, ERE-E1b-Luc, and either 500 ng SMRT_short or control (pCR3.1) expression vector followed by treatment with vehicle or 1 nm E2 for 24 h. The M_r of SMRT_short is approximately 175 kDa. Values represent the average ± sem of three independent experiments. *, P < 0.01 in comparison with control E2 values. D, HeLa cells were transfected with 250 ng expression vectors for control, SMRT_short, or SRC-3 alone or in combination in addition to ERα and ERE-E1b-Luc. Cells were subsequently treated with vehicle or E2 for 24 h. Values represent the average ± sem of four independent experiments. *, P < 0.01 in comparison with control E2 values.