Methylation pattern of the promoters of the 11p15 mucin genes in expressing and non-expressing epithelial cancer cell lines. Mapping of methylated cytosines was carried out by (a) MS–PCR and (b and c) bisulfite-treated genomic DNA sequencing. Numbering refers to the proximal transcription start site of each gene (broken arrows). Horizontal thick bars indicate CpG islands. Vertical bars indicate CpG sites. Five individual clones were analysed per CpG site and cell line. (b) For each gene, analyses were performed in one expressing (+) and one non-expressing (–) cell line. (c) For MUC2 and MUC5B, analyses were performed in proliferating (PC) and confluent (CC) HT-29 5F7 cells. Black circles represent methylated cytosines and open circles represent unmethylated cytosines. The bigger circles indicate CpG sites that were studied by MS–PCR. Gray circles indicate partially methylated cytosines. Key CpG methylated sites are topped with a star and their position in the promoter is indicated.