title: Natural C-independent expression of restriction endonuclease in a C protein-associated restriction-modification system.
abstract: Restriction-modification (R-M) systems are highly prevalent among bacteria and archaea, and appear to play crucial roles in modulating horizontal gene transfer and protection against phage. There is much to learn about these diverse enzymes systems, especially their regulation. Type II R-M systems specify two independent enzymes: a restriction endonuclease (REase) and protective DNA methyltransferase (MTase). Their activities need to be finely balanced in vivo Some R-M systems rely on specialized transcription factors called C (controller) proteins. These proteins play a vital role in the temporal regulation of R-M gene expression, and function to indirectly modulate the horizontal transfer of their genes across the species. We report novel regulation of a C-responsive R-M system that involves a C protein of a poorly-studied structural class - C.Csp231I. Here, the C and REase genes share a bicistronic transcript, and some of the transcriptional auto-control features seen in other C-regulated R-M systems are conserved. However, separate tandem promoters drive most transcription of the REase gene, a distinctive property not seen in other tested C-linked R-M systems. Further, C protein only partially controls REase expression, yet plays a role in system stability and propagation. Consequently, high REase activity was observed after deletion of the entire C gene, and cells bearing the ΔC R-M system were outcompeted in mixed culture assays by those with the WT R-M system. Overall, our data reveal unexpected regulatory variation among R-M systems.
authors.affiliation: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
authors.forename: Monika
authors.initials: M
authors.lastname: Rezulak
authors.affiliation: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
authors.forename: Izabela
authors.initials: I
authors.lastname: Borsuk
authors.affiliation: Department of Microbiology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland shamrock127@hotmail.com.
authors.forename: Iwona
authors.initials: I
authors.lastname: Mruk
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002954:Citrobacter / Q000235:genetics* / Q000378:metabolism; D004262:DNA Restriction Enzymes / Q000235:genetics* / Q000378:metabolism; D015257:DNA-Cytosine Methylases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal; D017930:Genes, Reporter; D007763:Lac Operon; D008969:Molecular Sequence Data; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D061785:Transcription Initiation, Genetic; D014169:Transformation, Bacterial
chemical_list: D001426:Bacterial Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015257:DNA-Cytosine Methylases; D004262:DNA Restriction Enzymes