Exogenous Sp1 induces the EGFR promoter and potentiates YY1 induction; expression of exogenous wild-type p53 suppresses EGFR promoter induction by YY1 and Sp1 in normal HKc. (a) Normal HKc were transiently co-transfected with the pGL3-EGFR promoter construct (1.5 μg per well) and the pcDNA 3.1 YY1 expression plasmid or the pcDNA 3.1 control plasmid (10 ng per well), along with the pPacSp1 expression vector or the pPac control plasmid (100 ng per well) and pRL-Null (10 ng per well). Cells were harvested 48 h post-transfection for dual-luciferase assays. (b) Normal HKc were transiently co-transfected with the pGL3-EGFR promoter construct (1.5 μg per well), and the pcDNA 3.1 wild-type p53 expression plasmid, or the pcDNA 3.1 control plasmid (500 ng per well), along with the pPacSp1 expression vector or the pPac control plasmid (100 ng per well) and pRL-Null (10 ng per well). Cells were harvested 48 h post-transfection for dual-luciferase assays. EGFR, epidermal growth factor receptor; HKc, human keratinocytes; YY1, Yin Yang 1.