Abstract: Objective To study the effect of acute low dose radiation on DNA methylation and DNA methyltransferase(DNMT) in liver and bone marrow of mice . Methods The C57BL/6 mice was irradiated by linear accelerator with X ray one time. the peripheral blood cells were made in 1、3、7、14 days after radiation, Then these mice were killed , liver and BMNC was exacted. The DNA methylation levels of whole gene were detected by HPLC, the expression of DNMT1、DNMT3A and DNMT3B were detected by Western blot(WB). Results Compared with those in the normal group, the numbers of peripheral leukocyte and platelet was decreased significantly in the radiation group, the peripheral leukocyte in the first day dropped to the lowest and platelet fell to lowest in the third day, they all were not returned to normal in the 14rd. the DNA methylation levels of radiation group was decreased significantly, but with the increase of time, the methylation level returned to normal. the expression of DNMT1 and DNMT3A were increased significantly in the radiation group, they all were not returned to normal in the 14rd,the expression of DNMT3B were increased significantly, but returned to normal in 7rd day. Conclusion Acute low dose radiation can decrease the methylation levels of DNA and the expression of DNMTs.

Key words: low dose radiation, DNA methylation, DNA methyltransferase, epigenetics