Tailored Watson-Crick Pairing Partners for Xanthosine in RNA

Area of Science:

• RNA chemistry and molecular biology
• Nucleic acid modifications
• Synthetic biology

Background:

• Deamination of guanosine produces xanthosine (X)-containing RNA, a process analogous to A-to-I editing.
• The biological roles and chemical impacts of X-modified RNA are not well understood.
• Exploring novel base pairing interactions is crucial for understanding RNA function.

Purpose of the Study:

• To investigate the interactions of xanthosine (X) with synthetic pyrimidine nucleobases.
• To synthesize and characterize RNA duplexes containing novel base pairs involving X.
• To assess the stability and structural properties of these novel RNA base pairs.

Main Methods:

• Synthesis of RNA containing 2,4-diaminopyrimidine C-nucleoside kappa (K) and 2-iminocytidine (2imC).
• RNA solid-phase synthesis using phosphoramidite chemistry for K-modified RNA.
• Development of 2imC synthesis via 2-thiocytidine intermediate and OsO₄/NH₄Cl treatment.
• Analysis of duplex stability using melting temperature (Tm) measurements.
• Structural determination using nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography.

Main Results:

• Stable RNA duplexes were formed with K-X and 2imC-X base pairs.
• These novel base pairs exhibited significantly higher melting temperatures compared to X-C, X-U, A-U, and G-U pairs.
• Structural analyses confirmed the tridendate Watson-Crick geometry of the K-X base pair in an RNA double helix.

Conclusions:

• The synthesized K-X and 2imC-X base pairs demonstrate enhanced stability in RNA duplexes.
• These novel base pairs have the potential to expand the RNA genetic alphabet for use in decoding processes.
• Further research is needed to explore their biochemical and cellular applications.