Four-stranded DNA? Not double-stranded? DNA is generally double-stranded, but it has an exception. Due to an increase in advanced technology and the creation of an antibody that targets four-stranded DNA, it has been proven that four-stranded DNA is present in human cells by researchers. Four-stranded DNA can form in the guanine rich region of the DNA. Hence, the scientific name for the DNA structure is G-quadruplex.
DNA G-quadruplex. Photographed by Jean-Paul Rodriguez
Guanine is one of the four building blocks of DNA, and the others being: adenine, cytosine, and thymine. The oxygen molecules of Guanine are exposed when the G-quadruplex forms, and to stabilize the structure, a cation (positively charged ion) is present at the centre of the structure. In addition, the four guanine molecules are held together by hydrogen bonds in planar arrangement.
There has been an increase of attention for the research of four-stranded DNA since 1962. Before the experiment of Quantitative visualization of DNA G-quadruplex structures in human cells was done, four-stranded DNA in human cells was just a theory. Even though G-quadruplex was made in test tubes and found in single-cellular life, there was no direct proof that G-quadruplex can be formed in human cells. In the experiment mentioned above, researchers found four-stranded DNA in regulatory regions of human DNA, such as promoters, enhancers, repressors, and untranslated regions. In addition, telomeres (a region of DNA that protects the deterioration of DNA) also show motifs of G-quadruplex. From where G-quadruplex can be found, it can be inferred that G-quadruplex has potential functions of regulating DNA replication, transcription, and stabilizing chromosome.
The experiment further explored the presence of G-quadruplex throughout the development of human cells and found that it is most abundant when a human cell is rapidly dividing. Therefore, the researchers think there is a relationship between G-quadruplex and the presence of cancerous cells. New possible therapies for cancers may be formed by the disruption of G-quadruplex formation.
Much more research and detailed studies need to be done for G-quadruplex. The study of G-quadruplex could prove to have numerous beneficial possibilities, especially in the area of cancers. With the prospect of a potential key that may successfully create new treatments, researchers continue to have high hopes for the future.
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(Shirley) Yu Chen
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