Thermodynamic Stability of G-Quadruplexes: Impact of Sequence and Environment

G-quadruplexes have attracted growing interest in recent years due to their occurrence in vivo and their possible biological functions. In addition to being promising targets for drug design, these four-stranded nucleic acid structures have also been recognized as versatile tools for various technological applications. Whereas a large number of studies have yielded insight into their remarkable structural diversity, our current knowledge on G-quadruplex stabilities as a function of sequence and environmental factors only gradually emerges with an expanding collection of thermodynamic data. This minireview provides an overview of general rules that may be used to better evaluate quadruplex thermodynamic stabilities but also discusses present challenges in predicting most stable folds for a given sequence and environment.

Unraveling the Thermodynamics of the Folding and Interconversion of Human Telomere G-Quadruplexes

Why human telomere DNA fragments fold into different G-quadruplex structures with parallel, hybrid, and antiparallel strand orientations depending on the temperature and concentration of co-solutes remains poorly understood. Similarly, the formation of intermediate structures along the folding or interconversion pathways is not well understood. Herein, we address these questions by introducing a conceptual framework, based on the global thermodynamic analysis of DSC and CD spectroscopy data, which led to a detailed description of the topological phase space (phase diagram) of the stability of the human telomere fragment 5'-AGGG(TTAGGG)3 -3' (Tel22). This framework clarifies the driving forces of quadruplex folding and interconversion processes over a wide range of temperatures and ion (K(+) , Na(+) ) and polyethylene glycol (PEG) concentrations and demonstrates their linkage to the human telomere DNA structural features.

G-rich sequence-specific recognition and scission of human genome by PNA/DNA hybrid G-quadruplex formation

Hole in one: A single peptide nucleic acid (PNA) effectively targets the G-rich region in double-stranded DNA through formation of a PNA/DNA hybrid G-quadruplex. Only one target site in the whole human genome was selectively cleaved by the hybrid G-quadruplex. Such site-selective scission of DNA is central to gene manipulation for molecular biology, biotechnology, and therapy.