Novel m4C modification in type I restriction-modification systems
We identify a new subgroup of Type I Restriction-Modification enzymes that modify cytosine in one DNA strand and adenine in the opposite strand for host protection. Recognition specificity has been determined for ten systems using SMRT sequencing and each recognizes a novel DNA sequence motif. Previously characterized Type I systems use two identical copies of a single methyltransferase (MTase) subunit, with one bound at each half site of the specificity (S) subunit to form the MTase. The new m4C-producing Type I systems we describe have two separate yet highly similar MTase subunits that form a heterodimeric M1M2S MTase. The MTase subunits from these systems group into two families, one of which has NPPF in the highly conserved catalytic motif IV and modifies adenine to m6A, and one having an NPPY catalytic motif IV and modifying cytosine to m4C. The high degree of similarity among their cytosine-recognizing components (MTase and S) suggest they have recently evolved, most likely from the far more common m6A Type I systems. Type I enzymes that modify cytosine exclusively were formed by replacing the adenine target recognition domain (TRD) with a cytosine-recognizing TRD. These are the first examples of m4C modification in Type I RM systems.
Identification of the CTAG-recognizing restriction-modification systems MthZI and MthFI from Methanobacterium thermoformicicum and characterization of the plasmid-encoded mthZIM gene.
Two CTAG-recognizing restriction and modification (R/M) systems, designated MthZI and MthFI, were identified in the thermophilic archaeon Methanobacterium thermoformicicum strains Z-245 and FTF, respectively. Further analysis revealed that the methyltransferase (MTase) genes are plasmid-located in both strains. The plasmid pFZ1-encoded mthZIM gene of strain Z-245 was further characterized by su...متن کامل
The methylation of DNA bases plays an important role in numerous biological processes including development, gene expression, and DNA replication. Salmonella is an important foodborne pathogen, and methylation in Salmonella is implicated in virulence. Using single molecule real-time (SMRT) DNA-sequencing, we sequenced and assembled the complete genomes of eleven Salmonella enterica isolates fro...متن کامل
Site-specific methylation: effect on DNA modification methyltransferases and restriction endonucleases.
We present in Table I an updated list of the sensitivities of over 240 restriction endonucleases to the site-specific DNA modifications '14C, n-6C, h1"5C, and m6A, four modifications that are common in DNA prokaryotes, eukaryotes, and their viruses (Mc2,Mc5,Mc8,Mcl 1 ,Ne3,Ne4). Table II is a list of over 130 characterized DNA methyltransferases. A detailed list of cloned restrictionmodification...متن کامل
Genomic DNAs of 14 strains from seven species of the spirochete Leptospira were resistant to cleavage by the restriction endonuclease RsaI (5'-GTAC). A modified base comigrating with m4C was detected by chromatography. Genomic DNAs from other spirochetes, Borrelia group VS461, and Serpulina strains were not resistant to RsaI digestion. Modification at 5'-GTAm4C may occur in most or all strains ...متن کامل
A protein function is carried out by a specific domain localized at a specific position. In the present study, we report that, within a gene, a specific amino acid sequence can move between a certain position and another position. This was discovered when the sequences of restriction-modification systems within the bacterial species Helicobacter pylori were compared. In the specificity subunit ...متن کامل