Retron for the 67-Base Multicopy Single-Stranded DNA from Escherichia coli: A Potential Transposable Element Encoding Both Reverse Transcriptase and Dam Methylase Functions

• Published in: Proceedings of the National Academy of Sciences - PNAS 1990-12, Vol.87 (23), p.9454-9458
• Main Authors: Hsu, Mei-Yin, Inouye, Masayori, Inouye, Sumiko
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Bacteriophages; Base Sequence; Biological and medical sciences; Chromosome Mapping; Chromosomes; Chromosomes, Bacterial; Dams; DNA; DNA Transposable Elements; DNA, Single-Stranded - genetics; Escherichia coli - genetics; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; Genes; Genic rearrangement. Recombination. Transposable element; Genomes; Methyltransferases - genetics; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Nucleotide sequences; Open reading frames; Restriction Mapping; RNA-Directed DNA Polymerase - genetics; Sequence Homology, Nucleic Acid; Site-Specific DNA-Methyltransferase (Adenine-Specific); Transposons
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.87.23.9454

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.