Restriction and modification of deoxyarchaeosine (dG+)-containing phage 9?g DNA.
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ABSTRACT: E. coli phage 9?g contains the modified base deoxyarchaeosine (dG+) in its genome. The phage encodes its own primase, DNA ligase, DNA polymerase, and enzymes necessary to synthesize and incorporate dG+. Here we report phage 9?g DNA sensitivity to >200 Type II restriction endonucleases (REases). Among the REases tested approximately 29% generated complete or partial digestions, while the remaining 71% displayed resistance to restriction. Phage 9?g restriction fragments can be degraded by DNA exonucleases or ligated by T3 and T4 DNA ligases. In addition, we examined a number of cytosine and adenine methyltransferases to generate double base modifications. M.AluI, M.CviPI, M.HhaI, and M.EcoGII were able to introduce 5mC or N6mA into 9?g DNA as confirmed by partial resistance to restriction and by liquid chromatography-mass spectrometry. A number of wild-type E. coli bacteria restricted phage 9?g, indicating natural restriction barriers exist in some strains. A BlastP search of GenBank sequences revealed five glutamine amidotransferase-QueC homologs in Enterobacteria and Pseudomonas phage, and distant homologs in other phage and bacterial genomes, suggesting that dG+ is not a rare modification. We also mapped phage 9?g DNA packaging (pac) site containing two 21-bp direct repeats and a major terminase cleavage site in the phage genome.
SUBMITTER: Tsai R
PROVIDER: S-EPMC5567051 | biostudies-literature | 2017 Aug
REPOSITORIES: biostudies-literature
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