Global DNA Methylation Assay Kit (5 Methyl Cytosine, Colorimetric)

Global DNA Methylation Assay Kit (5 Methyl Cytosine, Colorimetric) (ab233486) contains all reagents necessary for the quantification of global DNA methylation. In this assay, DNA is bound to strip-wells that are specifically treated to have a high DNA affinity. The methylated fraction of DNA is detected using capture and detection antibodies and then quantified colorimetrically by reading the absorbance in a microplate spectrophotometer. The percentage of methylated DNA is proportional to the OD intensity measured.

DNA methylation occurs by the covalent addition of a methyl group at the 5-carbon of the cytosine ring by DNA methyltransferases, resulting in 5-methylcytosine (5-mC). In somatic cells, 5-mC is found almost exclusively in the context of paired symmetrical methylation of the dinucleotide CpG, whereas in embryonic stem (ES) cells, a substantial amount of 5-mC is also observed in non-CpG contexts. Levels of 5-mC are variable in animal genomes, ranging from undetectable amounts in some insects to about 2% of total DNA in vertebrates. The level of 5-mC in plants generally accounts for 0.5-2% and can be as high as 8% of total DNA in some other species. The biological importance of 5-mC as a major epigenetic modification in phenotype and gene expression has been recognized widely. For example, global decrease in 5-mC content (DNA hypomethylation) is likely caused by methyldeficiency due to a variety of environmental influences, and has been proposed as a molecular marker in multiple biological processes such as cancer. It has been well demonstrated that the decrease in global DNA methylation is one of the most important characteristics of cancer.

A few novel modified nucleotides, 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC) and 5carboxycytosine (5-caC), have been detected in human and mouse tissues as well as embryonic stem cells. In mammals, these modified nucleotides can be generated by iterative oxidation of 5methylcytosine, a reaction mediated by the TET family of enzymes.

A line of evidence shows that these modified cytosines play a critical role in regulating gene function by impacting DNA methylation structures and patterns.