title: Temperate Myxococcus xanthus phage Mx8 encodes a DNA adenine methylase, Mox.
abstract: Temperate bacteriophage Mx8 of Myxococcus xanthus encapsidates terminally repetitious DNA, packaged as circular permutations of its 49-kbp genome. During both lytic and lysogenic development, Mx8 expresses a nonessential DNA methylase, Mox, which modifies adenine residues in occurrences of XhoI and PstI recognition sites, CTCGAG and CTGCAG, respectively, on both phage DNA and the host chromosome. The mox gene is necessary for methylase activity in vivo, because an amber mutation in the mox gene abolishes activity. The mox gene is the only phage gene required for methylase activity in vivo, because ectopic expression of mox as part of the M. xanthus mglBA operon results in partial methylation of the host chromosome. The predicted amino acid sequence of Mox is related most closely to that of the methylase involved in the cell cycle control of Caulobacter crescentus. We speculate that Mox acts to protect Mx8 phage DNA against restriction upon infection of a subset of natural M. xanthus hosts. One natural isolate of M. xanthus, the lysogenic source of related phage Mx81, produces a restriction endonuclease with the cleavage specificity of endonuclease BstBI.
authors.affiliation: Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow 83844-3052, USA.
authors.forename: V
authors.initials: V
authors.lastname: Magrini
authors.forename: D
authors.initials: D
authors.lastname: Salmi
authors.forename: D
authors.initials: D
authors.lastname: Thomas
authors.forename: S K
authors.initials: SK
authors.lastname: Herbert
authors.forename: P L
authors.initials: PL
authors.lastname: Hartzell
authors.forename: P
authors.initials: P
authors.lastname: Youderian
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D004279:DNA, Viral; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D005814:Genes, Viral; D008969:Molecular Sequence Data; D016941:Myxococcus xanthus / Q000821:virology*; D017386:Sequence Homology, Amino Acid; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000235:genetics* / Q000502:physiology; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: D004279:DNA, Viral; D014764:Viral Proteins; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C107143:mox protein, Bacteriophage Mx8; C034510:CTCGAG-specific type II deoxyribonucleases; C024388:CTGCAG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific