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Selection for short introns in highly expressed genes.
Cristian I Castillo-Davis1, Sergei L Mekhedov, Daniel L Hartl
1Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Nature Genetics
|July 23, 2002
Summary
Highly expressed genes have shorter introns to reduce the high cost of transcription. This natural selection favors shorter introns in eukaryotes, especially in humans, to minimize energy expenditure during gene expression.
Area of Science:
- Molecular Biology
- Genomics
- Evolutionary Biology
Background:
- Transcription is an energy-intensive process in eukaryotes.
- Long introns, common in mammals, increase the energetic cost of transcribing highly expressed genes.
Purpose of the Study:
- To investigate the relationship between gene expression levels and intron length in eukaryotes.
- To determine if natural selection favors shorter introns in highly expressed genes.
Main Methods:
- Analysis of gene expression and intron length data from Caenorhabditis elegans and Homo sapiens.
- Comparison of intron lengths in highly expressed genes versus lowly expressed genes.
Main Results:
- Introns in highly expressed genes are significantly shorter than those in lowly expressed genes across both species.
- The difference in intron length is more pronounced in humans (14-fold) than in C. elegans (2-fold).
- Intron density showed no strong correlation with gene expression levels.
Conclusions:
- Natural selection favors shorter introns in highly expressed genes to minimize the metabolic costs associated with transcription and splicing.
- Intron length is an adaptive trait influenced by gene expression levels and evolutionary pressures.