These methylases are of interest here for two reasons. First, some or all of the sites for a restriction endonuclease may be resistant to cleavage when isolated from strains expressing the Dam or Dcm methylases. This occurs because DNA is protected from cleavage when a particular base in the recognition site of a restriction endonuclease is methylated. The relevant base may be methylated by one of the E. colimethylases if the methylase recognition site overlaps the endonuclease recognition site. For example, plasmid DNA isolated from Dam+ E. coli is completely resistant to cleavage by MboI (NEB #R0147), which cleaves at GATC sites. The table below summarizes the possible overlaps and what is known about cleavability of DNA modified by Dam or Dcm. Almost all cloning strains are Dam+Dcm+, and many are M+EcoKI. For more detailed information about K methylation, consult REBASE, the restriction enzyme database