• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1280-1285
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• 2004

Retron is a prokaryotic genetic element, producing a short single-stranded DNA covalently linked to RNA (msDNA-RNA) by a reverse transcriptase (RT). In retron EC83, msDNA is further processed at between the 4th and the $5^{th}$ nucleotides, leaving a 79 nucleotide-long single-stranded DNA as a final product. To investigate this site-specific cleavage in msDNA synthesis, we purified the RT protein of retron EC83. Initially, RT ORF was cloned under the tac promoter, but the expression was very poor largely because of poor translation. In order to facilitate translation, the nucleotide sequence for the first nine amino acids was randomized with synonymous codons. This change of downstream sequence of translational initiation codon greatly affected the efficiency of translation. We could isolate clones which greatly increased RT production, and their sequences were compared to those of the low producers. The overproduced protein was purified and was shown to have RT activity.

• Genomics & Informatics
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• v.14 no.1
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• pp.29-33
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• 2016

A retron is a bacterial retroelement that encodes an RNA gene and a reverse transcriptase (RT). The former, once transcribed, works as a template primer for reverse transcription by the latter. The resulting DNA is covalently linked to the upstream part of the RNA; this chimera is called multicopy single-stranded DNA (msDNA), which is extrachromosomal DNA found in many bacterial species. Based on the conserved features in the eight known msDNA sequences, we developed a detection method and applied it to scan National Center for Biotechnology Information (NCBI) RefSeq bacterial genome sequences. Among 16,844 bacterial sequences possessing a retron-type RT domain, we identified 48 unique types of msDNA. Currently, the biological role of msDNA is not well understood. Our work will be a useful tool in studying the distribution, evolution, and physiological role of msDNA.

• Journal of Microbiology
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• v.42 no.3
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• pp.200-204
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• 2004

Retron is a prokaryotic genetic element that produces multicopy single-stranded DNA covalently linked to RNA (msDNA) by a reverse transcriptase. It was found that cells producing a large amount of msDNA, rather than those that did not, showed a higher rate of mutation. In order to understand the molecular mechanism connecting msDNA production to the high mutation rate the protein patterns were compared by two dimensional gel electrophoresis. Ten proteins were found to be differentially expressed at levels more than three fold greater in cells with than without msDNA, nine of which were identified by MALDI TOF MS. Eight of the nine identified proteins were repressed in msDNA-producing cells and, surprisingly, most were proteins functioning in the dissimilation of various carbon sources. One protein was induced four fold greater in the msDNA producing cells and was identified as a 30S ribosomal protein S2 involved in the regulation of translation. The molecular mechanism underlying the elevated mutation in msDNA-producing cell still remains elusive.

• Proceedings of the Zoological Society Korea Conference
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• 1994.10a
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• pp.252.1-252
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• 1994

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