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Summary
The Alu sequence in 7SL RNA predates mammalian evolution, appearing before species diverged. Mammalian Alu sequences likely originated from 7SL RNA through a deletion, suggesting they are processed 7SL RNA genes.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Genetics
Background:
- 7SL RNA is crucial for protein secretion, acting as a component of the signal recognition particle.
- Alu sequences are abundant repetitive DNA elements in humans and rodents.
- Human 7SL RNA contains an Alu sequence and a unique 7SL-specific region.
Purpose of the Study:
- To investigate the evolutionary origins of the Alu domain within 7SL RNA.
- To compare 7SL RNA sequences across different species to understand evolutionary relationships.
Main Methods:
- Determined the nucleotide sequence of Xenopus laevis 7SL RNA cDNA.
- Sequenced the 7SL RNA gene from Drosophila melanogaster.
- Performed sequence homology analysis between species.
Main Results:
- Xenopus laevis 7SL RNA shows 87% homology to human 7SL RNA.
- Drosophila melanogaster 7SL RNA exhibits 64% homology to both human and Xenopus 7SL RNA.
- Conserved regions homologous to both Alu and 7SL-specific sequences were found in Drosophila.
Conclusions:
- The Alu sequence in 7SL RNA evolved before mammalian radiation.
- Mammalian Alu sequences are proposed to be derived from 7SL RNA via deletion of the central 7SL-specific sequence.
- This suggests mammalian Alu sequences represent processed 7SL RNA genes.