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1: J Biol Chem. 2000 Aug 11;275(32):24893-9.
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A distinct sequence (ATAAA)n separates methylated and unmethylated domains at the 5'-end of the GSTP1 CpG island.

Millar DS, Paul CL, Molloy PL, Clark SJ.

Kanematsu Laboratories, Royal Prince Alfred Hospital, Missenden Road, Camperdown, New South Wales 2050, Australia.

What defines the boundaries between methylated and unmethylated domains in the genome is unclear. In this study we used bisulfite genomic sequencing to map the boundaries of methylation that flank the 5'- and 3'-ends of the CpG island spanning the promoter region of the glutathione S-transferase (GSTP1) gene. We show that GSTP1 is expressed in a wide range of tissues including brain, lung, skeletal muscle, spleen, pancreas, bone marrow, prostate, heart, and blood and that this expression is associated with the CpG island being unmethylated. In these normal tissues a marked boundary was found to separate the methylated and unmethylated regions of the gene at the 5'-flank of the CpG island, and this boundary correlated with an (ATAAA)(19-24) repeated sequence. In contrast, the 3'-end of the CpG island was not marked by a sharp transition in methylation but by a gradual change in methylation density over about 500 base pairs. In normal tissue the sequences on either side of the 5'-boundary appear to lie in separate domains in which CpG methylation is independently controlled. These separate methylation domains are lost in all prostate cancer where GSTP1 expression is silenced and methylation extends throughout the island and spans across both the 5'- and 3'-boundary regions.

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PMID: 10779522 [PubMed - indexed for MEDLINE]