Exclusion of glucosyl-hydroxymethylcytosine DNA containing bacteriophages is overcome by the injected protein inhibitor IPI* |
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Authors: | Bair Catherine L Rifat Dalin Black Lindsay W |
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Institution: | Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201-1503, USA. |
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Abstract: | The Escherichia coli isolate CT596 excludes infection by the Myoviridae T4 ip1(-) phage that lacks the encapsidated IPI* protein normally injected into the host with the phage DNA. Screening of a CT596 genomic library identified adjacent genes responsible for this exclusion, gmrS (942 bp) and gmrD (708 bp) that are encoded by a cryptic prophage DNA. The two genes are necessary and sufficient to confer upon a host the ability to exclude infection by T4 ip1(-) phage and other glucosyl-hydroxymethylcytosine (glc-HMC) Tevens lacking the ip1 gene, yet allow infection by phages with non-glucoslyated cytosine (C) DNA that lack the ip1 gene. A plasmid expressing the ip1 gene product, IPI*, allows growth of Tevens lacking ip1 on E. coli strains carrying the cloned gmrS/gmrD genes. Members of the Teven family carry a diverse and, in some cases, expanded set of ip1 locus genes. In vivo analysis suggests a family of gmr genes that specifically target sugar-HMC modified DNA have evolved to exclude Teven phages, and these exclusion genes have in turn been countered by a family of injected exclusion inhibitors that likely help determine the host range of different glc-HMC phages. |
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Keywords: | glc-HMC glucosylated hydroxymethylcytosine CTS capsid targeting sequence eop efficiency of plating DUF domain of unknown function MDS modification-dependent system |
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