Deoxyribozymes (DNAzymes) are artificial enzymes made of DNA that are evolved in the laboratory. DNAzymes can catalyze various reactions. They can, for example, cleave RNA in response to naturally modified nucleotides in the target RNA. This means RNA-cleaving DNAzymes could serve as selective sensors and catalysts to examine the modification state of RNA.

Claudia Höbartner and colleagues, University of Würzburg, Germany, have used in vitro selection to obtain RNA-cleaving DNAzymes that can be used to detect the native tRNA modification N⁶-isopentenyladenosine (i⁶A). N⁶-isopentenyladenosine (pictured in red) is a structural analogue of N⁶-methyladenosine (m⁶A), one of the most abundant mRNA modifications. DNAzyme candidates from a synthetic DNA library with 20 random nucleotides were selected for their ability to discriminate modified from unmodified RNA.

The team discovered the first deoxyribozyme that is strongly and specifically activated by a natural tRNA modification. This DNAzyme cleaved i⁶A-containing RNA at least 2500-fold faster than unmodified RNA, but was not activated by the related modified nucleotide m⁶A. These results show that modified RNA can strongly influence the catalytic activity of DNA.

• N⁶‐isopentenyladenosine in RNA determines the cleavage site of endonuclease deoxyribozymes,
  Anam Liaqat, Carina Stiller, Manuela Michel, Maksim V Sednev, Claudia Höbartner,
  Angew. Chem. Int. Ed. 2020.
  https://doi.org/10.1002/anie.202006218