Lower GC-content in editing exons: implications for regulation by molecular characteristics maintained by selection

Area of Science:

• Molecular Biology
• Genomics
• Evolutionary Biology

Background:

• RNA editing plays a crucial role in diversifying transcriptomes.
• Specific molecular features of RNA sequences can influence editing.
• The interplay between RNA editing and selection pressures is not fully understood.

Purpose of the Study:

• To investigate the molecular characteristics of RNA editing sites in Drosophila synaptotagmin I.
• To determine if these characteristics are associated with specific evolutionary pressures.
• To explore the relationship between molecular features, RNA editing, and purifying selection.

Main Methods:

• Comparative analysis of GC-content and GC3 in editing versus non-editing exons.
• Assessment of Gibbs free energy in different exon types.
• Sequence alignment and calculation of Ks and Ka/Ks ratios.
• Statistical validation using 47 experimentally-validated samples.

Main Results:

• Editing exons exhibit significantly lower GC-content and GC3, and higher Gibbs free energy compared to other exons.
• Sequence analysis indicates strong purifying selection acting on editing exons, limiting nucleotide divergence.
• These molecular characteristics are statistically correlated with RNA editing occurrence.

Conclusions:

• Lower GC-content and higher Gibbs free energy in editing exons are key molecular features associated with RNA editing in Drosophila synaptotagmin I.
• Rapidly ascending purifying selection acts on editing exons, constraining sequence variation.
• A potential link exists between DNA/RNA molecular characteristics, RNA editing, and purifying selection.