TSC-22 promoter hypermethylation attenuates gene expression. (A) Luciferase reporter assays in 293T cells transfected with variable lengths of the mouse (m) TSC-22 promoter indicate that strong promoter activity occurs within the −320-bp proximal region. (B) In vitro methylation of the −320-bp promoter of TSC-22 with Sss1 DNA methyltransferase (shaded bar) indicates that methylation of the −320-bp promoter region significantly inhibits TSC-22 promoter activity, which was detected by luciferase assays, compared with an unmethylated control construct (unshaded bar; P < .05). Error bars indicate standard deviations for triplicates in 1 of 3 representative experiments (A,B).