The Programmable Catalytic Core of 8-17 DNAzymes

Area of Science:

• Biochemistry
• Molecular Biology
• Catalysis

Background:

• 8-17 DNAzymes are in vitro-selected DNA catalysts that cleave RNA.
• Their catalytic activity is influenced by conserved residues and metal ions.
• Less conserved residues in bulge loops and internal stems offer opportunities for engineering.

Purpose of the Study:

• To program new catalytic cores for 8-17 DNAzymes.
• To investigate the impact of specific residues (W12, A15, A15.0) and internal stem sequences on DNAzyme activity.
• To derive and characterize a novel, highly active DNAzyme.

Main Methods:

• In vitro selection and engineering of 8-17 DNAzyme variants.
• Modification of bulge loop residues and internal stem sequences.
• Activity assays to evaluate catalytic cleavage of RNA.
• Metal ion, Na+, and pH dependence studies.

Main Results:

• The internal stem CTC-GAG was more favorable than CCG-GGC.
• An additional W12.0 residue significantly reduced DNAzyme activity.
• A15.0 incorporation led to a new DNAzyme, 17EM, with enhanced activity compared to 17E.
• 17EM exhibits optimal activity with Pb2+ and shows a specific metal ion preference (Pb2+ >> Zn2+ > Mn2+ > Ca2+ ≈ Mg2+).
• 17EM displays similar Na+ and pH dependence to other 8-17 DNAzymes.

Conclusions:

• 17EM is a novel, highly active member of the 8-17 DNAzyme family.
• The findings highlight the role of specific residues in modulating DNAzyme catalytic efficiency.
• 17EM demonstrates potential for application as a biosensor for RNA and metal ions, particularly Pb2+.