We determined the methylation state of the upstream CpG island of the μ-opioid receptor OPRM1 promoter region in 198 African-American and 203 Hispanic subjects. The upstream OPRM1 CpG island is located from nucleotides −93 to +27 (relative to the A of the ATG translation start site). Sixteen CpG dinucleotide sites are located within this region at −93, −90, −80, −71, −60, −50, −32, −25, −18, −14, −10, +12, +23, +27, +53, and +84. There are three potential Sp1-binding sites within this amplified region. One potential Sp1-binding site spans the −18 and the −14 CpG sites, another spans the +12 CpG site, and a third spans the +84 CpG dinucleotide site.
