Regulation of bacterial type II restriction-modification (R-M) systems

Type II restriction-modification (R-M) systems encode two separate enzymes: a restriction endonuclease (R) and a DNA methyltransferase (M). The action of the DNA sequence-specific methyltransferase protects the host DNA from cleavage by an associated restriction enzyme. The function of type II restriction-modification system regulation is generally assumed to be prevention of bacterial cell auto-restriction. The R and M genes must be regulated in such a way that the cell's own DNA is fully protected before restriction endonuclease activity appears. There a variety of control mechanisms that ensure the correct temporal expression of R-M genes. Unfortunately, the regulation mechanisms have not been well explored thus far. The understanding of the expression regulation of R-M genes is important and may influence the direction of research on new therapeutic methods.