title: Methylation-dependent DNA restriction in Bacillus anthracis.
abstract: Bacillus anthracis, the causative agent of anthrax, is poorly transformed with DNA that is methylated on adenine or cytosine. Here we characterize three genetic loci encoding type IV methylation-dependent restriction enzymes that target DNA containing C5-methylcytosine (m5C). Strains in which these genes were inactivated, either singly or collectively, showed increased transformation by methylated DNA. Additionally, a triple mutant with an ~30-kb genomic deletion could be transformed by DNA obtained from Dam(+)Dcm(+)E. coli, although at a low frequency of ~10(-3) transformants/10(6)cfu. This strain of B. anthracis can potentially serve as a preferred host for shuttle vectors that express recombinant proteins, including proteins to be used in vaccines. The gene(s) responsible for the restriction of m6A-containing DNA in B. anthracis remain unidentified, and we suggest that poor transformation by such DNA could in part be a consequence of the inefficient replication of hemimethylated DNA in B. anthracis.
authors.affiliation: Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Sitaraman
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
mesh_terms: D000225:Adenine / Q000378:metabolism; D001408:Bacillus anthracis / Q000201:enzymology / Q000235:genetics*; D003596:Cytosine / Q000378:metabolism; D019175:DNA Methylation; D004262:DNA Restriction Enzymes / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D010957:Plasmids; D014170:Transformation, Genetic
chemical_list: D003596:Cytosine; D004262:DNA Restriction Enzymes; D000225:Adenine