The inhibitory effect of PIAS3_82-132 on MITF and STAT3 transcriptional activity. (A) NIH-3T3 cells were cotransfected with an expression plasmid containing MITF, with a MITF luciferase reporter gene containing the mMCP-6 promoter, and with an expression plasmid containing either PIAS3_1-628 or PIAS3_82-132. Mean ± SE of 4 experiments is shown. (B) NIH-3T3 cells were cotransfected with the STAT3 luciferase reporter gene (M67), with an expression plasmid containing STAT3, and with expression plasmids containing either PIAS3_1-628 or PIAS3_82-132. Cells were then treated with IL-6/IL-6R for 6 hours, with untreated cells as the control. One representative of 3 experiments is shown. (C) RBL cells were nuclear transfected with the STAT3 luciferase reporter gene (M67), and with expression plasmids containing either PIAS3_1-628 or PIAS3_82-132. Mean ± SE of 4 experiments is shown. In all cases, luciferase activity of lysed cells was measured and normalized against protein concentration. For each transfection, the total DNA concentration was kept constant by complementing with the empty vector pcDNA.