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Four-stranded DNA seen in human cells

Posted by on January 21, 2013
A molecular model of the G-quadruplex and visualisation of the structure inside living human cells

A molecular model of the G-quadruplex and visualisation of the structure inside living human cells.

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.

2 Responses to Four-stranded DNA seen in human cells

  1. Cory

    The discovery of the structure of DNA is one of the most important findings to date in the world of molecular biology. From this discovery stemmed numerous other findings that explain things that could only be theorized before. The experiments that they had to perform were difficult and tedious especially, since they were not the only ones trying to discover it. I’ve learned about the experiments and scientists numerous times in past biology classes. With the discovery of the processes behind transcription and translation, so much more has been explained. These ideas, while taking place on such a small scale are immensely important to life as we know it. This new finding opens up some interesting ideas that could be further researched. This discovery could even result in the better understanding and even prevention or treatment of things such as cancer.

  2. Erica

    This is so interesting! I wonder if this has something to do with the reason why there is more guanine and cytosine in the gene-rich areas of the genome? It also raises other questions: for example, how many other structures are there that DNA makes that we have yet to discover? I’m also curious about how scientists first had the idea that the G-quadruplex may exist, and that they should try to create it in a lab. Cool article!