The G-Triplex DNA

摘要

Nucleic acids represent the alphabet of the cellular language and through their sequence and topology regulate vital cellular functions. In recent years, it has been found that many variations from the Watson-Crick duplex structure play key roles in many cellular processes. Examples are hairpins, cruciforms, parallel-stranded duplexes, triplexes, G-quadruplexes, and the i-motif. These structures can be formed by nucleotide sequences distributed throughout the whole human genome, their location is not random and often associated with human diseases. These complexes are formed from one to four strands, stabilized by base stacking and hydrogen bond interactions, with a variety of non-standard pairings. For instance, DNA triplexes can present G:G-C, A:A-T, C~+:G-C, and T:A-T pairings, with two strands in the standard Watson-Crick duplex structure (i.e. G-C and A-T) and the third one lying in the major groove of the duplex. In contrast, G-quadruplexes are four-stranded structures stabilized by stacking of two or more guanine tetrads (Figure 1).