The features of polyglutamine regions depend on their evolutionary stability

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genomics

Background:

• Polyglutamine (polyQ) regions are prevalent eukaryotic homorepeats.
• CAG-slippage influences polyQ length and codon usage.
• Expanded polyQ tracts are linked to neurodegenerative diseases, while normal polyQ mediate protein interactions.

Purpose of the Study:

• To investigate the evolutionary stability of polyglutamine regions across diverse taxa.
• To determine factors influencing polyQ stability, including codon usage, amino acid context, and structural conformation.
• To assess the impact of polyQ stability on protein-protein interaction capacity.

Main Methods:

• Comparative analysis of 60 proteomes from Insecta, Teleostei, Sauria, and Mammalia.
• Categorization of polyQ regions into stable, inserted (length variation), and mutated (sequence variation) groups.
• Examination of codon usage, amino acid context, and secondary structure surrounding polyQ regions.

Main Results:

• PolyQ regions were classified into stable, inserted, and mutated categories based on evolutionary dynamics.
• CAG-slippage was predominant in inserted polyQ of Sauria and Mammalia.
• PolyQ stability, rather than taxonomic group, was a key determinant of structural conformation and protein-protein interaction capacity.

Conclusions:

• Assessing polyQ function necessitates analyzing orthologous sequences alongside sequence data.
• Codon usage, amino acid context, structural conformation, and protein-protein interaction capacity are critically dependent on polyQ stability.
• Taxa-driven evolutionary analysis is crucial for a comprehensive understanding of polyglutamine region features.