- Multicopy single-stranded DNA
Multicopy single-stranded DNA (msDNA) is a type of extrachromosomal satellite DNA that consists of a single-stranded DNA molecule linked via a phosphodiester bond to a branched RNA molecule. The resultant structure possesses two stem-loop structures, and functions as both a primer and a template for the creation of more msDNA. It is known to encode a type of reverse transcriptase. Its function remains unknown even though many copies are present within cells.
Before the discovery of msDNA in Myxococcus xanthus, a species of soil-dwelling bacteria, it was thought that the enzymes known as reverse transcriptases (RT) existed only in eukaryotes and viruses. The discovery led to an increase in research of the area; as a result, msDNA was found to exist within certain strains of the bacterium Escherichia coli. Further research discovered similarities between the open reading frames of HIV-encoded reverse transcriptase and msDNA, and was later tested for reverse transcriptase activity and RNase H activity. It was found that both the RNase H domain and the enzyme reverse transcriptase are required in order for msDNA to replicate.
The discovery of msDNA has led to questions regarding where reverse transcriptase originated, as genes encoding for it have been found in prokaryotes, eukaryotes, and even viruses. After a DNA fragment coding for the production of msDNA in E. coli was discovered, it was suggested that bacteriophages might have been responsible for the introduction of the RT gene into E. coli. These discoveries suggest that reverse transcriptase played a role in the evolution of viruses from bacteria, with one hypothesis stating that, with the help of reverse transcriptase, viruses may have arisen as a breakaway msDNA gene that acquired a protein coat.
- Reverse Transcriptase in E.coli: msDNA — Mellon College of Science
- ^ Inouye S, Herzer PJ, Inouye M (February 1990). "Two independent retrons with highly diverse reverse transcriptases in Myxococcus xanthus". Proc. Natl. Acad. Sci. U.S.A. 87 (3): 942–5. doi:10.1073/pnas.87.3.942. PMC 53385. PMID 1689062. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=1689062.
- ^ Lampson BC, Inouye M, Inouye S (2005). "Retrons, msDNA, and the bacterial genome". Cytogenet. Genome Res. 110 (1-4): 491–9. doi:10.1159/000084982. PMID 16093702. http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=CGR20051101_4491.
- ^ Lampson BC, Sun J, Hsu MY, Vallejo-Ramirez J, Inouye S, Inouye M (February 1989). "Reverse transcriptase in a clinical strain of Escherichia coli: production of branched RNA-linked msDNA". Science 243 (4894 Pt 1): 1033–8. doi:10.1126/science.2466332. PMID 2466332. http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=2466332.
- ^ Hsu MY, Inouye M, Inouye S (December 1990). "Retron for the 67-base multicopy single-stranded DNA from Escherichia coli: a potential transposable element encoding both reverse transcriptase and Dam methylase functions". Proc. Natl. Acad. Sci. U.S.A. 87 (23): 9454–8. doi:10.1073/pnas.87.23.9454. PMC 55184. PMID 1701261. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=1701261.
- ^ Inouye S., Inouye M. (1993). "Bacterial Reverse Transcriptase". In Goff, Stephen; Skalka, Anna M.. Reverse transcriptase. Cold Spring Harbor monograph series. 23. Plainview, N.Y: Cold Spring Harbor Laboratory Press. ISBN 0-87969-382-7.
Types of nucleic acids ConstituentsNucleobases · Nucleosides · Nucleotides · Deoxynucleotides Ribonucleic acids
(coding and non-coding)
Deoxyribonucleic acids Nucleic acid analogues Cloning vectors
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