Convergent Evolution of Adenosine Aptamers Spanning Bacterial, Human, and Random Sequences Revealed by Structure-Based Bioinformatics and Genomic SELEX

SummaryAptamers are structured macromolecules in vitro evolved to bind molecular targets, whereas in nature they form the ligand-binding domains of riboswitches. Adenosine aptamers of a single structural family were isolated several times from random pools, but they have not been identified in genomic sequences. We used two unbiased methods, structure-based bioinformatics and human genome-based in vitro selection, to identify aptamers that form the same adenosine-binding structure in a bacterium, and several vertebrates, including humans. Two of the human aptamers map to introns of RAB3C and FGD3 genes. The RAB3C aptamer binds ATP with dissociation constants about 10 times lower than physiological ATP concentration, while the minimal FGD3 aptamer binds ATP only cotranscriptionally.

Graphical AbstractFigure optionsDownload high-quality image (239 K)Download as PowerPoint slideHighlights
► Adenosine aptamers are paradigms of convergent molecular evolution
► Structure-based search revealed this motif in bacterial and vertebrate genomes
► In vitro selection from a human genomic library yielded two more aptamers
► One of the human aptamers binds ATP exclusively cotranscriptionally