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Human piRNAs are under selection in Africans and repress transposable elements.
1Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
Molecular Biology and Evolution
|May 27, 2011
Summary
Piwi-interacting RNAs (piRNAs) in humans are under selective pressure, suggesting they help control transposable elements like LINE-1 and Alu. Population genomics reveals piRNA evolution and potential human-specific roles in genome regulation.
Area of Science:
- Genomics
- Molecular Biology
- Evolutionary Biology
Background:
- Piwi-interacting RNAs (piRNAs) are noncoding RNAs crucial for repressing transposable elements (TEs) in animal germ lines.
- Human genomes contain approximately 45% TE-derived sequences, including active LINE-1 and Alu elements, which contribute to mutations and variability.
Purpose of the Study:
- To investigate the function and evolution of piRNAs in humans using a population genomics approach.
- To explore the selective pressures on piRNA sequences and their relationship with TE activity in human populations.
Main Methods:
- Applied population genomics to analyze piRNA sequences in African populations.
- Mapped piRNA sequences to human TE sequences (LINE-1 and Alu) to assess correlations with TE subfamily age.
- Compared piRNA matches in human and mouse LINE-1 elements, focusing on the reverse transcriptase region.
Main Results:
- Found statistically significant evidence of selective constraint on piRNA sequences in African populations.
- Observed strong correlations between the age of LINE-1 and Alu subfamilies and the number of mapping piRNAs, supporting their role in TE repression.
- Identified a depletion of piRNA matches in the human LINE-1 reverse transcriptase region, suggesting a human-specific endogenous role.
Conclusions:
- PiRNA sequences are under selective constraint in humans, indicating a role in regulating transposable elements.
- Population genomics is a valuable tool for studying the evolution of rapidly evolving systems like piRNAs.
- The human LINE-1 element may possess a reverse transcriptase region with a function specific to humans.
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