Retron for the 67-base multicopy single-stranded DNA from Escherichia coli: a potential transposable element encoding both reverse transcriptase and Dam methylase functions.
The region (retron-Ec67) required for the biosynthesis of a branched-RNA-linked multicopy single-stranded DNA (msDNA-Ec67) from a clinical isolate of Escherichia coli was mapped at a position equivalent to 19 min on the K-12 chromosome. The element containing the retron consisted of a unique 34-kilobase sequence that was flanked by direct repeats of a 26-base-pair sequence found in the K-12 chromosomal DNA. This suggests that the 34-kilobase element was probably integrated into the E. coli genome by a mechanism related to transposition or phage integration. In the 34-kilobase sequence an open reading frame of 285 residues was found, which displays 44% sequence identity with the E. coli Dam methylase. Interestingly, there are three GATC sequences, the site of Dam methylation, in the promoter region of the gene for reverse transcriptase.
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Department of Biochemistry, Robert Wood Johnson Medical School, Rutgers, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Inouye
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Inouye
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004251:DNA Transposable Elements; D004277:DNA, Single-Stranded / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D008780:Methyltransferases / Q000235:genetics*; D008969:Molecular Sequence Data; D012194:RNA-Directed DNA Polymerase / Q000235:genetics*; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)
D004251:DNA Transposable Elements; D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli; D012194:RNA-Directed DNA Polymerase