Methylation pattern of the IL-1α promoter and intron IV in IL-1α–producing keratinocytes as determined by bisulfite sequencing. The level of methylation is expressed as the percentage of methylated CpGs (black bars) and unmethylated CpGs (white bars). (A) Methylation pattern of 14 CpGs (–13 through +1) located in the proximal promoter and 5′ UTR was analyzed by 3 separate PCR fragments as described in “Materials and methods,” based on at least 10 cloned fragments. (B) Methylation pattern of 13 CpGs in intron IV (+17 through +29), based on at least 10 cloned fragments.