Expression Of EcoRII R-M Genes In E.coli And Effect Of EcoRII(M) Specific Methylation On Normal And Tumor Cells

Restriction-modification systems comprise pairs of opposing intra-cellular enzyme activities: an endodeoxyribonuclease (R) and a DNA-methyltransferase(M) .which occur exclusively in bacteria.The main function of R-M systems is to protect cells from foreign DNA molecules,particularly bacteriophages.A large number of R and M emzymes have been used in the field of modern molecular biology,in the meantime,theoretical research on R-M themselves has also made important progress in protein-DNA interaction,regulation of gene expression, and mechanism of antivirus in procaryote. In 1990s,the focus of theoretical study has been shifted from R enzymes on to M enzymes. DNA methylation in mammalian cells is involved in many biological functions.and closely related to development and progress of cancer. Procaryotic M enzymes as model molecule play an important role in studying mechanism of methylation and demethylation.Preliminary objective of this study was to transfer R-M genes into mammalian cells and observe whether they could resist eucaryotic viruses as in procaryotic cells. In former study we had analysed procaryotic expression of R-M genes, but in later study we found that M enzyme could not produce complete methylation in mammalian genomic DNA,that is,it could not effectively protect host cells from R enzymes. However ,the specific methylation of M enzyme could complement general hypomethylation in tumor cells,and appeared to suppress the growth of tumor,this blazed a new pathway for anticancer study in aspect of correcting epigenetic abnormality.The research was divided into two sections. Section I: Identification of EcoRII R-M genes and expression in E.coli. Section II: Effect of EcoRII(M)...