CpG sites and Msp I/Hpa II sites in the human MDR1 promoter region. (Top) The CpG sites are represented by short vertical bars. The positions of exons 1 and 2 are indicated as closed boxes. The 978-bp fragment, the 450-bp and 777-bp fragments, and the 327-bp and 401-bp fragments are generated from the templates with completely methylated, partially methylated, and without methylatedMsp I/Hpa II sites by Pst I/Hpa II digestion. The position corresponding to these fragments are indicated. (Middle) The Msp I/Hpa II recognition sites are represented by short vertical bars. (Bottom) PCR primers used in the methylation analysis. MM2 and MM4 are methylation-sensitive primer pairs, and MC2 is a positive control primer pair.