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Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids

The nuclear genomes of euglenids contain three types of introns: conventional spliceosomal introns, nonconventional introns for which a splicing mechanism is unknown (variable noncanonical borders, RNA secondary structure bringing together intron ends), and so-called intermediate introns, which comb...

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Autores principales: Milanowski, Rafał, Karnkowska, Anna, Ishikawa, Takao, Zakryś, Bożena
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935182/
https://www.ncbi.nlm.nih.gov/pubmed/24296662
http://dx.doi.org/10.1093/molbev/mst227
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author Milanowski, Rafał
Karnkowska, Anna
Ishikawa, Takao
Zakryś, Bożena
author_facet Milanowski, Rafał
Karnkowska, Anna
Ishikawa, Takao
Zakryś, Bożena
author_sort Milanowski, Rafał
collection PubMed
description The nuclear genomes of euglenids contain three types of introns: conventional spliceosomal introns, nonconventional introns for which a splicing mechanism is unknown (variable noncanonical borders, RNA secondary structure bringing together intron ends), and so-called intermediate introns, which combine features of conventional and nonconventional introns. Analysis of two genes, tubA and tubB, from 20 species of euglenids reveals contrasting distribution patterns of conventional and nonconventional introns—positions of conventional introns are conserved, whereas those of the nonconventional ones are unique to individual species or small groups of closely related taxa. Moreover, in the group of phototrophic euglenids, 11 events of conventional intron loss versus 15 events of nonconventional intron gain were identified. A comparison of all nonconventional intron sequences highlighted the most conserved elements in their sequence and secondary structure. Our results led us to put forward two hypotheses. 1) The first one posits that mutational changes in intron sequence could lead to a change in their excision mechanism—intermediate introns would then be a transitional form between the conventional and nonconventional introns. 2) The second hypothesis concerns the origin of nonconventional introns—because of the presence of inverted repeats near their ends, insertion of MITE-like transposon elements is proposed as a possible source of new introns.
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spelling pubmed-39351822014-02-26 Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids Milanowski, Rafał Karnkowska, Anna Ishikawa, Takao Zakryś, Bożena Mol Biol Evol Discoveries The nuclear genomes of euglenids contain three types of introns: conventional spliceosomal introns, nonconventional introns for which a splicing mechanism is unknown (variable noncanonical borders, RNA secondary structure bringing together intron ends), and so-called intermediate introns, which combine features of conventional and nonconventional introns. Analysis of two genes, tubA and tubB, from 20 species of euglenids reveals contrasting distribution patterns of conventional and nonconventional introns—positions of conventional introns are conserved, whereas those of the nonconventional ones are unique to individual species or small groups of closely related taxa. Moreover, in the group of phototrophic euglenids, 11 events of conventional intron loss versus 15 events of nonconventional intron gain were identified. A comparison of all nonconventional intron sequences highlighted the most conserved elements in their sequence and secondary structure. Our results led us to put forward two hypotheses. 1) The first one posits that mutational changes in intron sequence could lead to a change in their excision mechanism—intermediate introns would then be a transitional form between the conventional and nonconventional introns. 2) The second hypothesis concerns the origin of nonconventional introns—because of the presence of inverted repeats near their ends, insertion of MITE-like transposon elements is proposed as a possible source of new introns. Oxford University Press 2014-03 2013-12-02 /pmc/articles/PMC3935182/ /pubmed/24296662 http://dx.doi.org/10.1093/molbev/mst227 Text en © The Author 2013. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. http://creativecommons.org/licenses/by-nc/3.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
spellingShingle Discoveries
Milanowski, Rafał
Karnkowska, Anna
Ishikawa, Takao
Zakryś, Bożena
Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title_full Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title_fullStr Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title_full_unstemmed Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title_short Distribution of Conventional and Nonconventional Introns in Tubulin (α and β) Genes of Euglenids
title_sort distribution of conventional and nonconventional introns in tubulin (α and β) genes of euglenids
topic Discoveries
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3935182/
https://www.ncbi.nlm.nih.gov/pubmed/24296662
http://dx.doi.org/10.1093/molbev/mst227
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