Demethylation (the transfer of the methyl group to another compound) is a common process, and reagents that undergo this reaction are called methylating agents. Common methylating agents are dimethyl sulfate, methyl iodide, and methyl triflate. Methanogenesis, the source of natural gas, arises via a demethylation reaction. Together with ubiquitin and phosphorylation, methylation is a major biochemical process for modifying protein function.  The field of epigenetics focuses on the influence of methylation on gene expression.