DNA Methylation in Prokaryotes: Regulation and Function

Abstract

Methylation of DNA in prokaryotes is known since the 1950s, but its role is still elusive and therefore under intense investigation. Differently from eukaryotes, the most important methylation in bacteria takes place on adenines (in position N6). The enzymes responsible for DNA methylation are often associated with restriction enzymes acting as a defense mechanism against foreign DNA (Restriction-Modification or R-M system). Other methyltransferases are solitary that function independently of the presence of a cognate restriction enzyme and are mostly involved in controlling replication of chromosome, DNA mismatch repair systems, or modulating gene expression. This is the case of the methylase Dam in gamma-proteobacteria or CcrM in alpha-proteobacteria. In this chapter, we will discuss the role of the R-M system and the activity of Dam and CcrM.