Structure of a Stable G-Hairpin

Area of Science:

• Structural Biology
• Biochemistry
• Genetics

Background:

• G-rich DNA sequences are prevalent in telomeres and can form non-canonical structures.
• Understanding these structures is crucial for comprehending telomere maintenance and genomic stability.
• Previous studies have suggested complex folding patterns for G-rich oligonucleotides.

Purpose of the Study:

• To determine the atomic resolution structure of a stable G-hairpin formed by a native yeast DNA sequence.
• To elucidate the folding principles and base-pairing mechanisms governing G-rich oligonucleotide structures.
• To explore the implications for predicting natural DNA structures and designing artificial DNA elements.

Main Methods:

• X-ray crystallography was used to obtain the atomic resolution structure.
• An 11-nucleotide G-rich oligonucleotide (5'-d(GTGTGGGTGTG)-3') from Saccharomyces cerevisiae telomeric DNA was synthesized.
• Thermodynamic stability analysis was performed to assess the structural integrity.

Main Results:

• The study reports the first atomic resolution structure of a stable G-hairpin from a native DNA sequence.
• The DNA adopts a novel mixed parallel/antiparallel fold-back structure stabilized by dynamic G:G base pairs.
• The structure exhibits a complex topology with a central backbone chain reversal and 3'-to-5' terminal stacking.

Conclusions:

• The findings reveal novel principles of G-rich oligonucleotide folding, challenging previous assumptions about their complexity.
• The discovered structure has implications for predicting natural DNA recognition elements and designing artificial ones.
• The study highlights the intricate folding landscapes of short DNA single strands.