The structure of an RNA dodecamer shows how tandem U-U base pairs increase the range of stable RNA structures and the diversity of recognition sites

Area of Science:

• Structural biology
• Biochemistry
• Molecular biology

Background:

• Non-canonical base pairs are crucial for RNA structure and function.
• Tandem U-U base pairs are frequently observed and can stabilize RNA duplexes, contrasting with single U-U pairs.

Purpose of the Study:

• To elucidate the structural basis for the stability of tandem U-U base pairs in RNA duplexes.
• To investigate the conformational impact of tandem U-U base pairs on RNA structure.

Main Methods:

• X-ray crystallography was used to determine the structure of an RNA dodecamer containing tandem U-U base pairs.
• Analysis of atomic coordinates to assess base stacking, hydrogen bonding, and backbone torsion angles.

Main Results:

• The crystal structure of GGCGCUUGCGUC revealed a duplex with tandem U-U base pairs.
• These U-U pairs induced an 11-12 degree bend in the duplex due to conformational changes at the interfaces.
• Despite the bend, base stacking was preserved, and two hydrogen bonds per base pair contributed to structural stability.

Conclusions:

• Tandem U-U base pairs can form stable RNA structures distinct from canonical A-form RNA.
• These structures offer potential interfaces for specific RNA-RNA or RNA-protein recognition.
• The unusual hydrogen-bonding patterns in the grooves may serve as recognition sites.