Extensive mis-splicing of a bi-partite plant mitochondrial group II intron |
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Authors: | Helen Elina Gregory G. Brown |
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Affiliation: | Department of Biology, McGill University, Montreal, Quebec H3A 1B1, Canada |
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Abstract: | Expression of the seed plant mitochondrial nad5 gene involves two trans-splicing events that remove fragmented group II introns and join the small, central exon c to exons b and d. We show that in both monocot and eudicot plants, extensive mis-splicing of the bi-partite intron 2 takes place, resulting in the formation of aberrantly spliced products in which exon c is joined to various sites within exon b. These mis-spliced products accumulate to levels comparable to or greater than that of the correctly spliced mRNA. We suggest that mis-splicing may result from folding constraints imposed on intron 2 by base-pairing between exon a and a portion of the bi-partite intron 3 downstream of exon c. Consistent with this hypothesis, we find that mis-splicing does not occur in Oenothera mitochondria, where intron 3 is further fragmented such that the predicted base-pairing region is not covalently linked to exon c. Our findings suggest that intron fragmentation may lead to mis-splicing, which may be corrected by further intron fragmentation. |
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