Guanine tetrad
Structure in molecular biology
From Wikipedia, the free encyclopedia
Structure
Right: Three guanine tetrads contributing to the structure of a G-quadruplex
A guanine tetrad (also known as a G-tetrad or G-quartet) is a square planar structure composed of four nonadjacent guanine bases interacting through Hoogsteen-style hydrogen bonding. [1][2] Two or more guanine tetrads can interact through π-π stacking to form G-quadruplexes.[1][3][4] Guanine tetrads are formed by RNA or DNA sequences rich in guanine, such as GGGGC.[5]
Stabilization
Guanine tetrads are stabilized by central monovalent cations, such as lithium, sodium, potassium, rubidium, or caesium.[6][7] They are more stable when stacked due to intermolecular forces between layers.[8] The sugar-phosphate backbone of DNA can also assist in stability.[1]
Biological Functions
Guanine tetrads can influence recombination, replication, and transcription.[1][2] For instance, guanine tetrads are found in the promoter region of the Myc family of oncogenes.[9] They also function in immunoglobulin class switching and may play a role in the genome of HIV.[10] Guanine tetrads appear frequently in the telomeric regions of DNA.[3]
Guanine tetrads may play a role in the dimerization of non-endogenous RNAs to facilitate the replication of some viruses.[5] Guanine tetrads dimerize through their 5' ends since it is more energetically favorable.[11]