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Published on: May 13, 2016
Balancing selection and the evolution of functional polymorphism in Old World monkey TRIM5alpha.
Ruchi M Newman1, Laura Hall, Michelle Connole
1Department of Microbiology and Molecular Genetics, Harvard Medical School, Southborough, MA 01772, USA.
Summary
Primate TRIM5alpha evolution involves balancing selection, maintaining ancient genetic variations across species. This suggests complex evolutionary pressures beyond simple lineage-specific adaptations for TRIM5alpha.
Area of Science:
- Evolutionary biology
- Primate genetics
- Immunology
Background:
- The retroviral restriction factor TRIM5alpha shows significant sequence diversity across primate species.
- Previous hypotheses suggested this diversity arose from ancient, lineage-specific positive selection events.
Purpose of the Study:
- To investigate the role of within-species genetic variation in the evolution of TRIM5alpha.
- To explore the evolutionary mechanisms shaping TRIM5alpha diversity in primates.
Main Methods:
- Analysis of TRIM5alpha genetic polymorphism in two geographically distinct Old World monkey species.
- Identification of shared polymorphisms predating speciation events.
- Functional assays to assess the impact of allelic variation on retroviral restriction.
Main Results:
- Extensive polymorphism was found within species, including shared polymorphisms predating speciation.
- Sequence variations, both silent and nonsynonymous, were concentrated in specific TRIM5alpha domains.
- Functional assays demonstrated that similar alleles conferred differential restriction against a panel of retroviruses.
Conclusions:
- The primate TRIM5alpha locus has evolved under balancing selection, maintaining ancient polymorphisms for millions of years.
- This balancing selection acts alongside lineage-specific adaptations, indicating a complex evolutionary history for TRIM5alpha.
- TRIM5alpha represents a rare example of long-term balancing selection in primates, similar to the MHC.
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