title: Conformational transition of a hairpin structure to G-quadruplex within the WNT1 gene promoter.
abstract: The role of G-quadruplexes (G4s) in biological systems has been widely studied. It is found that they have an important function in gene transcription and regulation. In this work, we have identified two topologies of hairpin and G4 structures formed by a native G-rich sequence (WT22: 5'-GGGCCACCGGGCAGGGGGCGGG-3') from the WNT1 promoter region using nuclear magnetic resonance (NMR) spectroscopy. With the help of site-specific isotope labeling, the topologies of these two structures are unambiguously characterized. Circular dichroism and NMR results are analyzed to determine the kinetics associated with the potassium ion-induced hairpin-to-G4 transition, which is very slow-on the time scale of 4800 s-compared to the previously reported folding kinetics of G4 formation. In addition, the free energies of the unfolding of these two structures are obtained using differential scanning calorimetry. Combining the kinetic and thermodynamic data, we have established the free energy landscape of this two-state folding system. Considering that similar conformational change may exist in other native G-rich sequences, this work highlights an important hairpin to G4 conformational transition which can be used in manipulation of gene regulation or ligand modulation in vivo.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei 106, Taiwan, R.O.C.
authors.forename: Margaret Hsin-Jui
authors.initials: MH
authors.lastname: Kuo
authors.forename: Zi-Fu
authors.initials: ZF
authors.lastname: Wang
authors.forename: Ting-Yuan
authors.initials: TY
authors.lastname: Tseng
authors.forename: Ming-Hao
authors.initials: MH
authors.lastname: Li
authors.forename: Shang-Te Danny
authors.initials: ST
authors.lastname: Hsu
authors.forename: Jing-Jer
authors.initials: JJ
authors.lastname: Lin
authors.forename: Ta-Chau
authors.initials: TC
authors.lastname: Chang
mesh_terms: D054856:G-Quadruplexes; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D051155:Wnt1 Protein / Q000235:genetics*
chemical_list: D051155:Wnt1 Protein