Figure 7.

Regulation of PDGFRA transcription by ErbB4 activity. (A) SK-N-MC human neuroblastoma cells were treated for 48 h with or without control or ErbB4-specific siRNAs. Relative PDGFRA and ERBB4 mRNA expression was analyzed by real-time RT-PCR and normalized to the expression of the reference gene β-actin. (B) MCF-7 breast cancer cells were transfected with the PDGFRA promoter luciferase reporter constructs pSLA4PDGFRαluc–441/+118 (441), pSLA4PDGFRαluc–944/+118 (944), or pSLA4PDGFRαluc–1253/+118 (1253) together with a plasmid encoding EGFP. Cells starved for 16 h were treated for 2 h with or without 80 ng/ml NRG-1 to activate ErbB4 or for 18 h with 10 μM retinoic acid (RA) as a positive control known to stimulate PDGFRA promoter activity. Columns represent relative luciferase activity of promoter constructs normalized by the EGFP fluorescence signal (no treatment = 100% for each experiment). (C) MCF-7 cells expressing pSLA4PDGFRαluc–1253/+118 were treated for 48 h with or without control or ErbB4-specific siRNAs, starved for 16 h, and treated for 2 h with 0 or 80 ng/ml NRG-1. Columns represent relative luciferase activity of promoter constructs normalized by the EGFP fluorescence signal. (D) MCF-7 cells expressing pSLA4PDGFRαluc–1253/+118 were treated for 48 h with control siRNA or siRNAs targeting the indicated transcription factors (TF), starved for 16 h and treated for 2 h with 0 or 80 ng/ml NRG-1. PDGFRA promoter activity was determined as in C. The values represent the effect of NRG-1 treatment as percentages of the control siRNA sample. The transcription factor mRNA expression levels, as determined by real-time RT-PCR, are shown relative to control siRNA treatment (TF mRNA %).