title: A novel host-specific restriction system associated with DNA backbone S-modification in Salmonella.
abstract: A novel, site-specific, DNA backbone S-modification (phosphorothioation) has been discovered, but its in vivo function(s) have remained obscure. Here, we report that the enteropathogenic Salmonella enterica serovar Cerro 87, which possesses S-modified DNA, restricts DNA isolated from Escherichia coli, while protecting its own DNA by site-specific phosphorothioation. A cloned 15-kb gene cluster from S. enterica conferred both host-specific restriction and DNA S-modification on E. coli. Mutational analysis of the gene cluster proved unambiguously that the S-modification prevented host-specific restriction specified by the same gene cluster. Restriction activity required three genes in addition to at least four contiguous genes necessary for DNA S-modification. This functional overlap ensures that restriction of heterologous DNA occurs only when the host DNA is protected by phosphorothioation. Meanwhile, this novel type of host-specific restriction and modification system was identified in many diverse bacteria. As in the case of methylation-specific restriction systems, targeted inactivation of this gene cluster should facilitate genetic manipulation of these bacteria, as we demonstrate in Salmonella.
authors.affiliation: Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200030, China.
authors.forename: Tiegang
authors.initials: T
authors.lastname: Xu
authors.forename: Fen
authors.initials: F
authors.lastname: Yao
authors.forename: Xiufen
authors.initials: X
authors.lastname: Zhou
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
authors.forename: Delin
authors.initials: D
authors.lastname: You
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D004269:DNA, Bacterial / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism; D013045:Species Specificity; D013455:Sulfur / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D013455:Sulfur