Study of a hammerhead ribozyme containing 2'-modified adenosine residues

Area of Science:

• Biochemistry
• Molecular Biology
• Organic Chemistry

Background:

• Hammerhead ribozymes are crucial RNA molecules with catalytic activity.
• Modifications to nucleosides can alter RNA structure and function.
• Understanding these alterations is vital for RNA-based therapeutics and research.

Purpose of the Study:

• To synthesize 2 -fluoro-2 -deoxyadenosine (2 -FA) and 2 -deoxy-adenosine (2 -dA).
• To incorporate these modified nucleosides into hammerhead ribozymes.
• To investigate the impact of these modifications on ribozyme catalytic activity.

Main Methods:

• Improved synthesis of 2 -FA from adenosine.
• Conversion of 2 -FA to phosphoramidite for automated RNA synthesis.
• Incorporation of 2 -FA and 2 -dA into hammerhead ribozymes.
• Kinetic analysis (kcat/Km) of modified and unmodified ribozymes.

Main Results:

• Successfully synthesized 2 -FA and 2 -dA and incorporated them into hammerhead ribozymes.
• Ribozymes with complete substitution of adenosine with 2 -FA or 2 -dA showed a significant decrease in catalytic efficiency (kcat/Km).
• This reduction in activity was attributed to a decrease in kcat and was a cumulative effect of modified nucleosides, not specific to any single residue.

Conclusions:

• The presence of 2 -FA or 2 -dA at adenosine positions in hammerhead ribozymes impairs catalytic function.
• The observed decrease in catalytic efficiency is a result of accumulated modifications throughout the RNA structure.
• These findings have implications for designing modified ribozymes for specific applications.