In chemistry, methylation, means that a substituent methyl group or atom or a substrate, the addition of a methyl group. Methylation is not a methyl group, which is one embodiment of a plurality of carbon chains and alkylation with substitution of a hydrogen atom. These terms are used in the field of biological science chemistry, biochemistry, and soil science in general. In biological systems, methylation is catalyzed by such enzymes may be involved regulating heavy metals and gene expression, and changes in the regulation of RNA metabolism and protein function is methylated. The methylation of heavy metals, may occur outside of biological systems. Chemical methylation of tissue samples is a method to reduce artifacts histological staining identified.

There will be caused by one of the methylation of proteins or DNA methylation contributes to inherit epigenetic methylated. DNA methylation in vertebrates, CpG sites typically (- guanine – cytosine guanine of the DNA sequence directly followed by a cytosine phosphate site, ie,) occur in. 5 – In the conversion to methyl cytosine, this methylation results. Formation of the CpG Me is catalyzed by the enzyme DNA methyltransferase. Human DNA is about 80 to 90% of the unmethylated CpG sites, but the island of CpG is rich (approximately 65% ​​portion is composed of a CG) to, GC they are not methylated In some areas known as, is there. They are associated with 56% of the promoter of the gene of mammals, including genes expressed ubiquitously all. This is a cluster of CpG, 1 ~ 2% of the human genome has an inverse relationship between the transcriptional activity and CpG methylation. Typically, methylation of the protein is performed with an amino acid residue of arginine or lysine in the protein sequence. Arginine methylation of methyl groups of two to one of the (symmetric dimethylarginine) nitrogen two terminal nitrogen one or two times (or monomethyl arginine), or (asymmetric dimethylarginine) peptidyl methyl transferase by (PRMTs) once it is possible to. I can by lysine lysine methyltransferase, once, three times methylation or twice. Methylation of proteins are studied in histones most. Transfer of a methyl group from S-adenosylmethionine histone catalyzed by an enzyme called histone methyltransferase. Histones that are methylated on the remaining specific, you can act epigenetically to activate or inhibit gene expression. Methylation of proteins, is a kind of post-translational modification.

Pattern of methylation, has become an important research topic recently. The study, in normal tissues, it was found that the coding region of the CpG methylation gene poor, are localized primarily. In contrast, the promoter region of the gene, the density of CpG islands in the region is high, but not methylated. The whole genome methylation tumor is characterized by “disproportionation methyl” increasing the expression of DNA methyl transferase and involves methylation localized. The genome-wide hypomethylation, Have increased the degree of mutation, and the precipitated factor in carcinogenesis as evidence to suggest that it can lead to chromosomal instability Further, methylation status in the cell as a whole. It can be used as biomarkers for tumor formation, the methylation status of specific genes. For example, methylation π-class glutathione S-transferase gene (GSTP1), appears promising diagnostic indicators for prostate cancer.

In cancer, the dynamics of gene silencing genetic and epigenetic are very different. Somatic gene mutation, leading to the block in the case of a functional protein from the mutant allele. The selective advantage, if it is given to the cell, the cell clones all, shall not be able to produce the protein, resulting expand the tumor cells. In contrast, to mediate gene silencing gradually epigenetically. In order to enhance the reduction of protection of CpG islands adjacent to the spread of the island methylation and heterochromatin, which starts a subtle reduction in transcription. Ranging from copies of the gene in cells of various This loss leads to a gradual increase in CpG sites individually.

Previously, we generated a high sequence specificity tracks adjacent guanine residues that several mutagenesis thymidine bromodeoxyuridine in mammalian cells (for BrdU) in (DT) are shown. To determine whether there is a structural component of sequence specificity, we analyzed the stereochemical nature of the guanine residues in the sequence different contexts. I was evaluated by steric difference measures the reaction of methylation agent guanine individual residues of dimethyl sulfate (DMS). The results of this study, we have shown that there is a correlation between a strong inverse between the sensitivity of these residues for mutagenesis with the BrdU for dT and sensitivity of methylation of guanine residues in various DMS . These results, by the dT and BrdU mutagenesis, stereochemical characteristics of guanine residues in the sequence context different, suggesting that affect the sensitivity of the guanine residues thereof.