By Jess Devonport, Marketing and Communications Officer at the Society of Biology
2013 is the 60th anniversary of Watson and Crick’s famous paper describing the helical structure of DNA. The Society of Biology plans to celebrate this landmark discovery with a series of genetics themed events and activities, called Genetics: where have we come from and where are we going? In light of this anniversary and these celebrations, it is probably quite fitting, then, that scientists at the University of Cambridge have now shown that DNA can exist in four-stranded “quadruple helix” structures.
The image of the double helix has become so iconic it’s almost synonymous with biology; two sugar-phosphate backbones spiralling around each other, connected by pairs of adenine and thymine, and cytosine and guanine, the nucleotide bases. The quadruple helix, or G-quadruplex, is rich in guanine and forms a compact square shape that interrupts the DNA strand.
This type of four-stranded DNA has been previously made in the lab by folding guanine-rich synthetic DNA; it has been speculated that these structures may form in living cells as the high amounts of guanine make then highly stable in near-physiological conditions. Now, researchers have visualised G-quadruplex structures in the genome of living human cells.
What does this mean for cell biology and disease?
It is quite likely that naturally-occuring G-quadruplex structures will have an important biological function; it has already been shown that the concentration of these structures is linked to DNA replication.
Telomeres, guanine-rich structures that protect the ends of chromosomes, are likely to contain G-quadruplex structures. Small molecules may be targeted to bind to the structures and disrupt the stability of the telomere, preventing DNA replication and cell proliferation.
The research group’s experiments also showed that these structures could occur at other guanine-rich areas of the genome. It’s possible that they may be involved in regulating genes and cellular process, and may give insight into the development of diseases such as cancer.
Professor Shankar Balasubramanian from University of Cambridge Department of Chemistry, who led the research, commented, “The research indicates that quadruplexes are more likely to occur in genes of cells that are rapidly dividing, such as cancer cells. For us, it strongly supports a new paradigm to be investigated – using these four-stranded structures as targets for personalised treatments in the future”. For more information about the discovery and its implications see University of Cambridge Research News.