Abstract
Methylations of DNA typically occur at CpG island in the promoter region of genes resulting in the decrease of transcription. DNA methylation status has been studied in association with carcinogenesis and aging. Biological relevance of changes of methylation pattern in the genomic DNA to cellular responses of chronic radiation exposure. In addition, whether the change of methylation pattern influences radiation sensitivity of cells or not is not determined. In order to understand the relationships between radiation exposure and the changes of methylation pattern, methylation sensitive arbitrarily primed PCR (MSAP-PCR) was performed using genomic DNA from parental HepG2 cells , other that from 3 sub-cell lines established by long-term exposure to X-rays, and that of radioresistant HepG2-8960-R cells. Compared with HepG2, we cloned 17 genomic regions where methyaltion status was changed in other sub-cell lines.. Of these, 4 regions were part of so-called genomic CpG island. Interestingly, 2 of them were related to the potassium ion channel (PIC). Since decrease of PIC activity is reported after exposure to low dose of X-rays, MSAP-PCR adopted in this study is suggested to be useful for the study of the relationship between DNA methylation and radiation exposure. We are now underway to investigate the changes of gene expressions cloned in this study and their biological significances.
