Tissue-specific methylation in the 5' flanking region of the gamma-glutamyl transpeptidase gene.

We have studied the relationship between the methylation and the expression of the gamma-glutamyl transpeptidase gene in adult rat liver and kidney. In the liver, where the level of expression is very low, the 5' flanking region of the gene appeared fully methylated, whereas in the kidney, where the gene is expressed at the highest level, it is undermethylated. In addition, kidney chromatin showed a DNase I hypersensitive site located near the origin of transcription. These results support a strong correlation between DNA undermethylation, DNase I sensitivity and tissue-specific gene expression.