Structure of two retrons of Escherichia coli and their common chromosomal insertion site.
It has been shown that certain strains of myxobacteria and of Escherichia coli have a genetic element encoding a reverse transcriptase (RT). This element, called a 'retron', produces a covalently linked RNA-DNA compound (msDNA-RNA). Here, I report the complete nucleotide sequence of retron EC-86, the retron in E. coli B, together with its flanking regions. Retron EC-86 contains genes for msDNA-RNA (msd, and msr), a gene for RT (ret) and a gene for an open reading frame whose function is unknown. The upstream junction is composed of the sequence GCGCGCGC, but there are no direct or inverted repeats at the retron-host junctions. It is also shown that another retron of E. coli, EC-67, which was isolated originally from the clinical strain CL1 and was later found to be present also in a clinical E. coli isolate from Brazil, is inserted at the same chromosomal site as retron EC-86. Retron EC-67 contains only msd, msr, and ret. I suggest that these two retrons were independently inserted into the same site of their host strains via a novel mechanism of integration.
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Department of Microbiology, New York University Medical Center, New York 10016.
D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D002876:Chromosomes, Bacterial / Q000502:physiology; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004277:DNA, Single-Stranded / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D009876:Operon / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics*; D012194:RNA-Directed DNA Polymerase / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics
D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D012329:RNA, Bacterial; C058681:msDNA; D012194:RNA-Directed DNA Polymerase