Retronphage phi R73: an E. coli phage that contains a retroelement and integrates into a tRNA gene.
Some strains of Escherichia coli contain retroelements (retrons) that encode genes for reverse transcriptase and branched, multicopy, single-stranded DNA (msDNA) linked to RNA. However, the origin of retrons is unknown. A P4-like cryptic prophage was found that contains a retroelement (retron Ec73) for msDNA-Ec73 in an E. coli clinical strain. The entire genome of this prophage, named phi R73, is 12.7 kilobase pairs and is flanked by 29-base pair direct repeats derived from the 3' end of the selenocystyl transfer RNA gene (selC). P2 bacteriophage caused excision of the phi R73 prophage and acted as a helper to package phi R73 DNA into an infectious virion. The newly formed phi R73 closely resembled P4 as a virion and in its lytic growth. Retronphage phi R73 lysogenized a new host strain, reintegrating its genome into the selC gene of the host chromosome and enabling the newly formed lysogens to produce msDNA-Ec73. Hence, retron Ec73 can be transferred intercellularly as part of the genome of a helper-dependent retronphage.
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Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854.
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D001483:Base Sequence; D015139:Blotting, Southern; D002874:Chromosome Mapping; D003090:Coliphages / Q000235:genetics* / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005814:Genes, Viral; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D016366:Open Reading Frames; D012343:RNA, Transfer / Q000235:genetics*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics
D004269:DNA, Bacterial; D004279:DNA, Viral; D015345:Oligonucleotide Probes; D012343:RNA, Transfer; D012194:RNA-Directed DNA Polymerase