Composite non-LTR retrotransposons in hominoid primates

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• Composite retrotransposons are prevalent across kingdoms, with complex variants found in hominoid primates.
• These elements (SVA, LAVA, PVA, FVA) integrate simple repeats, Alu fragments, VNTRs, and variable 3' domains, often derived from other retrotransposons.
• The precise assembly mechanism of VNTR-containing retrotransposons remained unclear, despite identifying a potential precursor (SVA2) in Rhesus genomes.

Purpose of the Study:

• To delineate the assembly order of components in VNTR-containing retrotransposons.
• To discuss the role of alternative splicing in co-mobilizing host RNA and exonization of composite retrotransposons.
• To explore structural determinants governing VNTR composite retrotransposon mobilization and lineage-specific expansion.

Main Methods:

• Comparative genomic analysis of retrotransposon sequences in hominoid primates.
• Phylogenetic reconstruction to infer evolutionary relationships and assembly pathways.
• Bioinformatic analysis of splicing patterns and structural features.

Main Results:

• An extinct precursor, "Alu-SVA2", likely acquired variant 3' ends through splicing.
• VNTR composite retrotransposons exhibit capacity for alternative splicing, co-mobilizing host RNA sequences.
• Structural features influence mobilization and expansion of specific retrotransposon families.

Conclusions:

• The study elucidates the assembly pathway of complex VNTR-containing retrotransposons in primates.
• Alternative splicing plays a crucial role in the functional evolution and mobilization of these elements.
• Understanding retrotransposon structure is key to explaining their lineage-specific expansion and impact on host genomes.