The perforin (PRF1) promoter (1411 bp) with locations of 34 CpG and several putative transcription factor binding sites. Ten CpGs are located in the enhancer element region, seven in the methylation-sensitive region (MSR) and 17 in the repetitive element region. "+1" indicates the transcription start site. Lower case letters from 'a -to- l' represent different transcription factor binding sites [14, 15]: a, inducer response motif; b, γ-IFN responsive element; c, CRE element; d, AP-2 element; e, TPA-responsive element; f, STAT5-responsive enhancer; g, CCAT box; h, C-fos enhancer; i, 19 homologous repeats; j, three repeats; k, two repeats; l, GC box. Upper case letters from 'A -to- K' represent amplicons (not scaled to size) designed to detect different CpG sites.