Figure 4. TAZ is a direct target of MRTF/SRF in breast cancer cells.

(A) HRG1 increased luciferase activity of TAZ promoter reporter. Luciferase activity of TAZ WT and CArG box mutant reporter were co-transfected with SV40-Rellina into the MCF7 cells. After 6 h transfection, medium was changed to serum free medium for overnight. 24 h later, cells were treated with HRG1 for 4 h and the relative luciferase activity was detected. **P < 0.01 by Student's t-test. (B) MRTF-A enhanced the luciferase activity of TAZ promoter reporter. TAZ reporters were co-transfected with MRTF-A expression plasmids as indicated in 293 cells. 24 h later, the relative luciferase activities were detected. **P < 0.01 by Student's t-test. (C) HRG1 promoted MRTF-A binding to the TAZ promoter. Serum starved and HRG1 treated (30 min) MCF7 cells were collected for ChIP-qPCR assay. ChIP assay were performed as previously described [28]. qPCR primers were designed based on the promoter sequence around the CArG box. **P < 0.01 by Student's t-test. (D) Knockdown SRF decreased the TAZ expression in MDA-MB-231. qPCR was performed to detect TAZ mRNA level in the cells transfected with indicated siRNA for 3 days. (E, F) MRTF-B promotes TAZ transcription in MDA-MB-231 cells. MDA-MB-231 cells were transfected with MRTF-B siRNA for 72 h. qPCR and western blot analysis were performed to detect the TAZ and MRTF-B level.