Transcription regulation of the EcoRV restriction–modification system

When a plasmid containing restriction-modification (R-M) genes enters a naïve host, unmodified host DNA can be destroyed by restriction endonuclease. Therefore, expression of R-M genes must be regulated to ensure that enough methyltransferase is produced and that host DNA is methylated before the endonuclease synthesis begins. In several R-M systems, specialized Control (C) proteins coordinate expression of the R and the M genes. C proteins bind to DNA sequences called C-boxes and activate expression of their cognate R genes and inhibit the M gene expression, however the mechanisms remain undefined. Here, we studied the regulation of gene expression in the C protein-dependent EcoRV system. We map the divergent EcoRV M and R gene promoters and we define the site of C protein-binding that is sufficient for activation of the EcoRV R transcription.