Formation of G-quadruplexes in poly-G sequences: structure of a propeller-type parallel-stranded G-quadruplex formed by a G₁₅ stretch.
Poly-G sequences are found in different genomes including human and have the potential to form higher-order structures with various applications. Previously, long poly-G sequences were thought to lead to multiple possible ways of G-quadruplex folding, rendering their structural characterization challenging. Here we investigate the structure of G-quadruplexes formed by poly-G sequences d(TTG(n)T), where n = 12 to 19. Our data show the presence of multiple and/or higher-order G-quadruplex structures in most sequences. Strikingly, NMR spectra of the TTG₁₅T sequence containing a stretch of 15 continuous guanines are exceptionally well-resolved and indicate the formation of a well-defined G-quadruplex structure. The NMR solution structure of this sequence revealed a propeller-type parallel-stranded G-quadruplex containing three G-tetrad layers and three single-guanine propeller loops. The same structure can potentially form anywhere along a long G(n) stretch, making it unique for molecular recognition by other cellular molecules.
School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
Anjali
A
Sengar
Brahim
B
Heddi
Anh Tuân
AT
Phan
D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D003848:Deoxyguanine Nucleotides / Q000737:chemistry; D054856:G-Quadruplexes; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011119:Polynucleotides / Q000737:chemistry; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013942:Thymine Nucleotides / Q000737:chemistry
D003848:Deoxyguanine Nucleotides; D011119:Polynucleotides; D013942:Thymine Nucleotides; D004247:DNA