In molecular biology, a guanine tetrad (also known as a G-tetrad or G-quartet) is a structure composed of four

guanine Guanine () ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is ca ...

bases in a square planar array. They most prominently contribute to the structure of

G-quadruplex In molecular biology, G-quadruplex secondary structures (G4) are formed in nucleic acids by sequences that are rich in guanine. They are helical in shape and contain guanine tetrads that can form from one, two or four strands. The unimolecular ...

es, where their hydrogen bonding stabilizes the structure. Usually, there are at least two guanine tetrads in a G-quadruplex, and they often feature Hoogsteen-style hydrogen bonding. Guanine tetrads are formed by sequences rich in guanine, such as GGGGC. They may also play a role in the dimerization of non-endogenous RNAs to facilitate the replication of some viruses. Guanine tetrads dimerize through their 5' ends since it is more energetically favorable. They can be stabilized by central

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s, such as lithium, sodium, potassium,

rubidium Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density hig ...

, or

cesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that ar ...

. However, they still form a variety of different structures. Guanine tetrads are not always stable, but the sugar-phosphate backbone of DNA can assist in stability of the guanine tetrads themselves. Guanine tetrads are more stable when stacked, as

intermolecular force An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles, e.g. a ...

s between each layers help stabilize them. Guanine tetrads can also influence recombination, replication, and transcription. For instance, guanine tetrads are found in the

promoter region In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein (mRNA), or can have a function in and of i ...

of the Myc family of

oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.

s. They also function in immunoglobulin class switching and may play a role in the genome of

HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immu ...

. Guanine tetrads appear frequently in the telomeric regions of DNA.

References

{{reflist, refs= {{Cite journal, last1=Kogut, first1=Mateusz, last2=Kleist, first2=Cyprian, last3=Czub, first3=Jacek, date=2016-04-20, title=Molecular dynamics simulations reveal the balance of forces governing the formation of a guanine tetrad-a common structural unit of G-quadruplex DNA, journal=Nucleic Acids Research, volume=44, issue=7, pages=3020–3030, doi=10.1093/nar/gkw160, issn=1362-4962, pmc=4838382, pmid=26980278 {{Cite journal, last1=Walsh, first1=K., last2=Gualberto, first2=A., date=1992-07-05, title=MyoD binds to the guanine tetrad nucleic acid structure, journal=The Journal of Biological Chemistry, volume=267, issue=19, pages=13714–13718, doi=10.1016/S0021-9258(18)42272-7, issn=0021-9258, pmid=1320026, doi-access=free {{Cite journal, last1=Sundquist, first1=Wesley, last2=Klug, first2=Aaron, date=1989, title=Telomeric DNA dimerizes by formation of guanine tetrads between hairpin loops, journal=Nature, volume=342, issue=6251, pages=825–829, doi=10.1038/342825a0, pmid=2601741, bibcode=1989Natur.342..825S, s2cid=4357161 {{Cite journal, last1=Meyer, first1=Michael, last2=Brandl, first2=Maria, last3=Sühnel, first3=Jürgen, date=2001-09-01, title=Are Guanine Tetrads Stabilized by Bifurcated Hydrogen Bonds?, journal=The Journal of Physical Chemistry A, volume=105, issue=35, pages=8223–8225, doi=10.1021/jp011179i, bibcode=2001JPCA..105.8223M, issn=1089-5639 {{Cite journal, last1=Yu, first1=H., last2=Li, first2=T., last3=Qiao, first3=W., last4=Chen, first4=Q., last5=Geng, first5=Y., date=2007, title=Guanine tetrad and palindromic sequence play critical roles in the RNA dimerization of bovine foamy virus, journal=Archives of Virology, volume=152, issue=12, pages=2159–2167, doi=10.1007/s00705-007-1047-5, issn=0304-8608, pmid=17712597, s2cid=19794444 {{Cite journal, last1=Kogut, first1=Mateusz, last2=Kleist, first2=Cyprian, last3=Czub, first3=Jacek, date=2019-09-20, title=Why do G-quadruplexes dimerize through the 5'-ends? Driving forces for G4 DNA dimerization examined in atomic detail, journal=PLOS Computational Biology, volume=15, issue=9, pages=e1007383, doi=10.1371/journal.pcbi.1007383, issn=1553-734X, pmc=6774569, pmid=31539370, bibcode=2019PLSCB..15E7383K {{Cite journal, last1=Azargun, first1=Mohammad, last2=Fridgen, first2=Travis D., date=2015-09-30, title=Guanine tetrads: an IRMPD spectroscopy, energy resolved SORI-CID, and computational study of M(9-ethylguanine)4+ (M = Li, Na, K, Rb, Cs) in the gas phase, journal=Physical Chemistry Chemical Physics, language=en, volume=17, issue=39, pages=25778–25785, doi=10.1039/C5CP00580A, pmid=25845669, bibcode=2015PCCP...1725778A, issn=1463-9084 {{Cite journal, last1=Fancui, first1=Meng, last2=Weiren, first2=Xu, last3=Chengbu, first3=Liu, date=May 2004, title=Theoretical study of incorporating 6-thioguanine into a guanine tetrad and their influence on the metal ion guanine tetrad, journal=Chemical Physics Letters, volume=389, issue=4, pages=421–426, doi=10.1016/j.cplett.2004.03.128, bibcode=2004CPL...389..421M {{Cite journal, title=Guanine Base Stacking in G-quadruplex Nucleic Acids, last1=Cj, first1=Lech, last2=B, first2=Heddi, date=2013-02-01, language=en, pmid=23268444, last3=At, first3=Phan, journal = Nucleic Acids Research, volume = 41, issue = 3, pages = 2034–46, doi = 10.1093/nar/gks1110, pmc = 3561957 {{Cite journal, last1=Phan, first1=Anh Tuân, last2=Kuryavyi, first2=Vitaly, last3=Gaw, first3=Hai Yan, last4=Patel, first4=Dinshaw J., date=Aug 2005, title=Small-molecule interaction with a five-guanine-tract G-quadruplex structure from the human MYC promoter, journal=Nature Chemical Biology, language=en, volume=1, issue=3, pages=167–173, doi=10.1038/nchembio723, pmid=16408022, pmc=4690526, issn=1552-4469 {{Cite journal, last1=Laughlan, first1=Gerard, last2=Murchie, first2=Alastair, last3=Norman, first3=David, date=22 Jul 1994, title=The High-Resolution Crystal Structure of a Parallel-Stranded Guanine Tetraplex, journal=American Association for the Advancement of Science, volume=265, issue=5171, pages=520–524, doi=10.1126/science.8036494, jstor=2884414, pmid=8036494, bibcode=1994Sci...265..520L, url=http://theses.gla.ac.uk/76305/1/13834037.pdf

External links

QGRS Mapper

QuadBase2
Molecular biology Molecular genetics Cell biology DNA G-quadruplex

See also

References

External links