Lineage-Specific Evolution, Structural Diversity, and Activity of R2 Retrotransposons in Animals.

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genetics

Background:

• Retrotransposons, particularly R2 elements, are crucial in genome evolution and disease, and are emerging tools for gene therapy.
• R2 retrotransposons target specific sites in 28S ribosomal RNA genes across eukaryotes.
• Previous studies on R2 retrotransposon distribution were limited in scope.

Purpose of the Study:

• To expand the known distribution of R2 retrotransposons across diverse taxonomic groups.
• To characterize the diversity of R2 domain architectures and identify potential candidates for genome engineering.
• To refine R2 classification based on evolutionary and functional insights.

Main Methods:

• Phylogenetic analysis of R2 retrotransposon sequences.
• Comparative analysis of R2 domain architectures and motifs.
• Functional assays of recombinant R2 proteins for target-primed reverse transcription.

Main Results:

• R2 retrotransposons were found in previously underrepresented groups, including ctenophores, amphibians, and reptiles.
• Diverse R2 domain architectures and motifs were identified, with many avian candidates for genome engineering.
• Phylogenetic analyses revealed two major R2 lineages with distinct DNA-binding and reverse transcriptase domain features.
• Recombinant R2 proteins demonstrated conserved site-specific target-primed reverse transcription despite varied domain architectures.

Conclusions:

• The study significantly expands the known distribution and diversity of R2 retrotransposons.
• Varied domain architectures supporting conserved site-specificity necessitate revised R2 classification criteria.
• These findings provide a foundation for understanding R2 evolution and developing novel gene insertion technologies.