Regulation of TXAS gene promoter activity by BACH1. A luciferase reporter construct containing a 535-bp fragment that included the transcription initiation site for the TXAS gene was transiently cotransfected with BACH1 or the Bach1-MafK chimeric protein expression plasmid (B1K) into QT6 fibroblasts by Lipofectamin (A), as well as the megakaryoblast cell line CMK11-5, by Nucleofector (B). The respective relative luciferase activity (mean ± SD of 4 independent experiments in QT-6, and 3 in CMK11-5) is shown. Each activity was standardized by reference to the β-galactosidase activity from the cotransfected expression plasmid, which was driven by the elongation factor 1 promoter.