title: The alternate expression of two restriction and modification systems.
abstract: Plasmids R124 and R124/3 carry genes coding for two different R-M systems and normally only one set of genes is expressed. These genes can be translocated to F plasmids that are compatible with the R factors and in strains carrying these F plasmids and an R factor a transacting regulatory mechanism switches off the expression of R-M genes on the introduced plasmid. Additionally the unexpressed genes on the introduced plasmid are expressed. The regulatory mechanism controlling the alternative expression of R124 and R124/3 R-M genes involves a physical rearrangement of DNA sequences.
mesh_terms: D003090:Coliphages / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005144:F Factor; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D010957:Plasmids; D011815:R Factors
chemical_list: D004269:DNA, Bacterial