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The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway

Group II introns are large ribozymes that require the assistance of intron-encoded or free-standing maturases to splice from their pre-mRNAs in vivo. They mainly splice through the classical branching pathway, being released as RNA lariats. However, group II introns can also splice through secondary...

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Autores principales: Monat, Caroline, Quiroga, Cecilia, Laroche-Johnston, Felix, Cousineau, Benoit
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Cold Spring Harbor Laboratory Press 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478347/
https://www.ncbi.nlm.nih.gov/pubmed/25956521
http://dx.doi.org/10.1261/rna.046367.114
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author Monat, Caroline
Quiroga, Cecilia
Laroche-Johnston, Felix
Cousineau, Benoit
author_facet Monat, Caroline
Quiroga, Cecilia
Laroche-Johnston, Felix
Cousineau, Benoit
author_sort Monat, Caroline
collection PubMed
description Group II introns are large ribozymes that require the assistance of intron-encoded or free-standing maturases to splice from their pre-mRNAs in vivo. They mainly splice through the classical branching pathway, being released as RNA lariats. However, group II introns can also splice through secondary pathways like hydrolysis and circularization leading to the release of linear and circular introns, respectively. Here, we assessed in vivo splicing of various constructs of the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis. The study of excised intron junctions revealed, in addition to branched intron lariats, the presence of perfect end-to-end intron circles and alternatively circularized introns. Removal of the branch point A residue prevented Ll.LtrB excision through the branching pathway but did not hinder intron circle formation. Complete intron RNA circles were found associated with the intron-encoded protein LtrA forming nevertheless inactive RNPs. Traces of double-stranded head-to-tail intron DNA junctions were also detected in L. lactis RNA and nucleic acid extracts. Some intron circles and alternatively circularized introns harbored variable number of non-encoded nucleotides at their splice junction. The presence of mRNA fragments at the splice junction of some intron RNA circles provides insights into the group II intron circularization pathway in bacteria.
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spelling pubmed-44783472016-07-01 The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway Monat, Caroline Quiroga, Cecilia Laroche-Johnston, Felix Cousineau, Benoit RNA Articles Group II introns are large ribozymes that require the assistance of intron-encoded or free-standing maturases to splice from their pre-mRNAs in vivo. They mainly splice through the classical branching pathway, being released as RNA lariats. However, group II introns can also splice through secondary pathways like hydrolysis and circularization leading to the release of linear and circular introns, respectively. Here, we assessed in vivo splicing of various constructs of the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis. The study of excised intron junctions revealed, in addition to branched intron lariats, the presence of perfect end-to-end intron circles and alternatively circularized introns. Removal of the branch point A residue prevented Ll.LtrB excision through the branching pathway but did not hinder intron circle formation. Complete intron RNA circles were found associated with the intron-encoded protein LtrA forming nevertheless inactive RNPs. Traces of double-stranded head-to-tail intron DNA junctions were also detected in L. lactis RNA and nucleic acid extracts. Some intron circles and alternatively circularized introns harbored variable number of non-encoded nucleotides at their splice junction. The presence of mRNA fragments at the splice junction of some intron RNA circles provides insights into the group II intron circularization pathway in bacteria. Cold Spring Harbor Laboratory Press 2015-07 /pmc/articles/PMC4478347/ /pubmed/25956521 http://dx.doi.org/10.1261/rna.046367.114 Text en © 2015 Monat et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society http://creativecommons.org/licenses/by-nc/4.0/ This article is distributed exclusively by the RNA Society for the first 12 months after the full-issue publication date (see http://rnajournal.cshlp.org/site/misc/terms.xhtml). After 12 months, it is available under a Creative Commons License (Attribution-NonCommercial 4.0 International), as described at http://creativecommons.org/licenses/by-nc/4.0/.
spellingShingle Articles
Monat, Caroline
Quiroga, Cecilia
Laroche-Johnston, Felix
Cousineau, Benoit
The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title_full The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title_fullStr The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title_full_unstemmed The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title_short The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway
title_sort ll.ltrb intron from lactococcus lactis excises as circles in vivo: insights into the group ii intron circularization pathway
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478347/
https://www.ncbi.nlm.nih.gov/pubmed/25956521
http://dx.doi.org/10.1261/rna.046367.114
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