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.
Department of Biochemistry, Robert Wood Johnson Medical School, Rutgers, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
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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