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These decoys are typically composed of a G-rich sequence that can form a stable G-quadruplex structure and a short linker region that can be modified to optimize their properties. [116] When introduced to cancer cells the decoy can intercept associated transcription factors and bind them leading to the regulation of gene expression.
G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine. [1] These structures are normally located at the telomeres (the ends of the chromosomes). The G-quadruplex can either be parallel or antiparallel depending on the loop configuration, which is a component of the structure.
In molecular biology, a guanine tetrad (also known as a G-tetrad or G-quartet) is a structure composed of four guanine bases in a square planar array. [ 1 ] [ 2 ] They most prominently contribute to the structure of G-quadruplexes , where their hydrogen bonding stabilizes the structure.
An individual motif usually consists of only a few elements, e.g., the 'helix-turn-helix' motif which has just three. Note that, while the spatial sequence of elements may be identical in all instances of a motif, they may be encoded in any order within the underlying gene. In addition to secondary structural elements, protein structural motifs ...
CpG is shorthand for 5'—C—phosphate—G—3' , that is, cytosine and guanine separated by only one phosphate group; phosphate links any two nucleosides together in DNA. . The CpG notation is used to distinguish this single-stranded linear sequence from the CG base-pairing of cytosine and guanine for double-stranded sequenc
The nucleotides 1-3 and 25-27 with an additional C4-G23 form a duplex motif, and the sequence ranging from G5 to G20 folds into a G-quadruplex structure with four connection loops: T9-A10, T18-T19, G13-C14-A15 and a one-nucleotide loop (T6). In the core of G-quadruplex motif, two G-tetrad planes are formed by G5-G7-G12-G16 and G8-G11-G17-G20.
The G-quartet typically binds monovalent cations such as potassium, while other bases can bind numerous other ligands such as hypoxanthine in a U-U-C-U quadruplex. [ 17 ] Along with these functions, the G-quadruplex in the mRNA around the ribosome binding regions could serve as a regulator of gene expression in bacteria . [ 19 ]
It is possible that these sequence stretches form G-quadruplex like structures, which can suppress the expression of the related genes. The complementary cytosine rich sequences, on the other strand, may adopt another similar four stranded structure, the i-motif, stabilized by cytosine:cytosine non-canonical base pairs.