Investigation of Structural diversity of G-quadruplexes: Potassium Concentration Effect

• Main Authors: Chang-Ting Lin, 林昶廷
• Other Authors: Ta-Chau Chang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/55628418340441845092

碩士 === 國立陽明大學 === 生醫光電工程研究所 === 98 === G-quadruplex (G4) structure, folded from Guanine-rich sequences, is a well known unique DNA secondary structure through Hoogsteen base pairing in the presence of monovalent cation. The importance of G4 structure is not only in human telomeres for protecting the ends of chromosomes, but also in several gene promoters for regulating gene expression. Here we have combined gel electrophoresis, circular dichroism (CD), thermal melting and differential scanning calorimetry (DSC) to study the possible coexistence of different types of G-quadruplexes in the presence of various concentrations of potassium cation (K+). Our results showed that an appreciable amount of high order G-quadruplex structures are detected in c-myc even at 1mM K+, and increases at high K+ concentration. Quantitative studies showed that the amounts of intramolecular G-quadruplex structure of c-myc and bcl2mid decrease as a function of K+ concentration. However, no discernible high order structures of human telomeric sequences up to 150 mM K+ solution. DSC melting studies reveal the existence of two different types of G-quadruplex structures of bcl2mid, each thermogram yields the thermodynamics parameters for each transition. Together with gel assays and thermodynamic profiles from DSC, we proposed that the high order G4 structure of bcl2mid existed in a bimolecular form.