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dc.creatorMohr, Georgen
dc.creatorGhanem, Emanen
dc.creatorLambowitz, Alan M.en
dc.identifier.citationMohr G, Ghanem E, Lambowitz AM (2010) Mechanisms Used for Genomic Proliferation by Thermophilic Group II Introns. PLoS Biol 8(6): e1000391. doi:10.1371/journal.pbio.1000391en
dc.description.abstractMobile group II introns, which are found in bacterial and organellar genomes, are site-specific retroelments hypothesized to be evolutionary ancestors of spliceosomal introns and retrotransposons in higher organisms. Most bacteria, however, contain no more than one or a few group II introns, making it unclear how introns could have proliferated to higher copy numbers in eukaryotic genomes. An exception is the thermophilic cyanobacterium Thermosynechococcus elongatus, which contains 28 closely related copies of a group II intron, constituting ~1.3% of the genome. Here, by using a combination of bioinformatics and mobility assays at different temperatures, we identified mechanisms that contribute to the proliferation of T. elongatus group II introns. These mechanisms include divergence of DNA target specificity to avoid target site saturation; adaptation of some intron-encoded reverse transcriptases to splice and mobilize multiple degenerate introns that do not encode reverse transcriptases, leading to a common splicing apparatus; and preferential insertion within other mobile introns or insertion elements, which provide new unoccupied sites in expanding non-essential DNA regions. Additionally, unlike mesophilic group II introns, the thermophilic T. elongatus introns rely on elevated temperatures to help promote DNA strand separation, enabling access to a larger number of DNA target sites by base pairing of the intron RNA, with minimal constraint from the reverse transcriptase. Our results provide insight into group II intron proliferation mechanisms and show that higher temperatures, which are thought to have prevailed on Earth during the emergence of eukaryotes, favor intron proliferation by increasing the accessibility of DNA target sites. We also identify actively mobile thermophilic introns, which may be useful for structural studies, gene targeting in thermophiles, and as a source of thermostable reverse transcriptases.en
dc.description.sponsorshipThis work was supported by National Institutes of Health grants GM037949 and GM037951 and Welch Foundation grant F-1607. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.en
dc.publisherPublic Library of Scienceen
dc.rightsAttribution 3.0 United Statesen
dc.subjectBacterial genomicsen
dc.subjectDNA sequencesen
dc.subjectGene predictionen
dc.subjectGenome evolutionen
dc.subjectPlasmid constructionen
dc.subjectSequence alignmenten
dc.subjectSequence motif analysisen
dc.titleMechanisms Used for Genomic Proliferation by Thermophilic Group II Intronsen
dc.description.departmentCellular and Molecular Biologyen

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Attribution 3.0 United States
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