Specific Methylation Status of the Entire CpG Island Is Not a Prerequisite for the Formation of an Inactive Chromatin at the Promoter Region in Cancer Cells

Abstract

It is well-recognized that DNA methylation causes gene silencing. However, although DNA methylation is closely associated with alterations in chromatin structure, it is not clear whether methylation at a particular locus contributes to the formation of an inactive chromatin structure. In this study, we have investigated the chromatin structure of the CpG island of the human CDH1 gene in cancer cells. The CDH1-CpG island was differentially methylated between silenced cells, however, DNase I hypersensitive site that are present in the expressing cell were commonly lost in silenced cells and transcription factors were excluded from their binding sites. These results demonstrate that formation of an inactive structure was not affected by heterogeneous methylation status of the CpG island.