By: Jocelyne Hilary and Stephanie Holz, Stuff Writers.
60 years after Watson and Crick’s discovery of the double helix, science is at it again. Researchers from Cambridge University have stumbled upon a new segment of DNA called a G-Quadruplex.
DNA contains four bases known as Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). These bases pair with each other like puzzle pieces to form the double helix. The double helix provides a blueprint for creating new materials cells use to function adequately.
A double helix of DNA bundles up into a warm, cozy little package called a chromosome located in the nucleus of cells. At each end of the chromosomes lie segments called telomeres which help protect the DNA inside. If you took all the DNA out of a single cell nucleus and laid it end to end, it would span around two meters long.
When a cell is ready to replicate, it must first make sure it has an extra copy of DNA so the second cell can also have the blueprint needed for it to function. This is done in a series of steps called the cell cycle. During a certain part of the cell cycle, known as the S phase, special regions of four stranded, box shaped DNA can be found. These are G-Quadruplexes.
G-Quadruplexes are named after their high Guanine content and four stranded structure. When these structures form by linking a series of Guanine together, they gather around the telomeres of chromosomes, which have been associated with certain cancers. If telomeres are damaged, they may not do as well at protecting DNA. When this happens, DNA can become damaged, therefore creating a higher risk of affecting the blueprint presented by DNA to cells.
A special enzyme called telomerase makes sure that the telomeres on every chromosome remain intact. However, when there are too many telomerases being expressed, cancer can occur. It was found that if an inhibitor was used to block DNA replication, G-Quadruplex levels go down. G-Quadruplexes are abundant during DNA replication, especially in rapidly dividing cells such as those with damage to DNA, which can mean cancerous mutations.
Casie Stronson, a biology major at the University said, “This just goes to show there are no limitations to science, and many new doors will open not only for the researchers involved, but for the student like me who thought we already knew everything there was to know about DNA. There’s clearly so much more to learn and to apply old knowledge to.”
Kayla Lee, another biology major, said, “Sometimes the importance of nitrogenous bases, particularly Guanine, is overlooked and never understood.”
The topic of G-Quadruplexes also appealed to Joseph Zundell. “G-Quadruplexes are more complex than most people understand. DNA isn’t just turned on and turned off like a light switch. There are multiple levels of regulation to provide feedback to other areas within the cell. So, a cancer medication that attempts to inhibit telomerase may interact, most likely, with other regulatory proteins (enzymes), or other components. If it weren’t this complex, life would cease to exist.”
It is the hope of many scientists that a drug can one day be produced to attack G-Quadruplexes in an attempt to halt the process of cell division in cancer cells. This would slow the growth of tumors and suppress malignancy.
