Arrest of Rolling Circle Amplification by Protein- Binding DNA Aptamers

Certain DNA polymerases, such as phi 29 DNA polymerase, can isothermally copy the sequence of a circular template round by round in a process known as rolling circle amplification (RCA), which results in super-long single-stranded (ss) DNA molecules made of tandem repeats. The power of RCA reflects the high processivity and the strand-displacement ability of these polymerases. In this work, the ability of phi 29DNAP to carry out RCA over circular templates containing a protein-binding DNA aptamer sequence was investigated. It was found that protein-aptamer interactions can prevent this DNA polymerase from reading through the aptameric domain. This finding indicates that protein-binding DNA aptamers can form highly stable complexes with their targets in solution. This novel observation was exploited by translating RCA arrest into a simple and convenient colorimetric assay for the detection of specific protein targets, which continues to showcase the versatility of aptamers as molecular recognition elements for biosensing applications.