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BMC Evol Biol. 2006 Sep 8;6:69.

Phase distribution of spliceosomal introns: implications for intron origin.

Author information

1
Frontier Science Research Center, University of Miyazaki 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan. ndhung@med.miyazaki-u.ac.jp

Abstract

BACKGROUND:

The origin of spliceosomal introns is the central subject of the introns-early versus introns-late debate. The distribution of intron phases is non-uniform, with an excess of phase-0 introns. Introns-early explains this by speculating that a fraction of present-day introns were present between minigenes in the progenote and therefore must lie in phase-0. In contrast, introns-late predicts that the nonuniformity of intron phase distribution reflects the nonrandomness of intron insertions.

RESULTS:

In this paper, we tested the two theories using analyses of intron phase distribution. We inferred the evolution of intron phase distribution from a dataset of 684 gene orthologs from seven eukaryotes using a maximum likelihood method. We also tested whether the observed intron phase distributions from 10 eukaryotes can be explained by intron insertions on a genome-wide scale. In contrast to the prediction of introns-early, the inferred evolution of intron phase distribution showed that the proportion of phase-0 introns increased over evolution. Consistent with introns-late, the observed intron phase distributions matched those predicted by an intron insertion model quite well.

CONCLUSION:

Our results strongly support the introns-late hypothesis of the origin of spliceosomal introns.

PMID:
16959043
PMCID:
PMC1574350
DOI:
10.1186/1471-2148-6-69
[Indexed for MEDLINE]
Free PMC Article

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