Mechanistic and Functional Links Between Histone Methylation and DNA Methylation

DNA methylation is a common mechanism of epigenetic regulation in eukaryotic organisms ranging from fungi to mammals. Genetic studies in model organisms have demonstrated the involvement of DNA methylation in a variety of biological processes. In mammals, DNA methylation patterns are established and maintained by three DNA methyltransferases: Dnmt3a, Dnmt3b, and Dnmt1. The basis of the specificity of the DNA methylation machinery and how DNA methylation patterns are regulated remain poorly understood. However, accumulating evidence suggests complex interplay between DNA methylation and other epigenetic mechanisms. Of particular interest is histone lysine methylation that has been shown to be tightly linked to DNA methylation in various systems. This chapter highlights the findings of several recent studies that provide insights into the mechanistic and functional interactions between histone methylation and DNA methylation.