Monthly Archives: January 2013

The DNA double helix has been an icon of science ever since it was first described by Francis Crick and James Watson in 1953.

But now researchers have found that human DNA can naturally wrap itself into a different shape a quadruple helix in a breakthrough that could point the way to new cancer treatments.

The new structure, which is composed of four strands wrapped around each other, was confirmed by scientists from Cambridge University the place where Crick and Watson made their famous discovery.

The quadruple DNA helix appears to be more common in cells that are rapidly dividing, indicating that it could be important in determining whether or not a cell becomes cancerous.

Professor Shankar Balasubramanian, who led the study published in the journal Nature Genetics, said: "It is quite a distinct structure to the double helix. It's a beautiful four-stranded helix that we know little about, but we are convinced it exists naturally.

"The quadruple helix DNA structure may well be the key to new ways of selectively inhibiting the proliferation of cancer cells. The confirmation of its existence in human cells is a real landmark.

"We are seeing links between trapping the quadruplexes with molecules and the ability to stop cells dividing, which is hugely exciting. The research indicates that quadruplexes are more likely to occur in genes of cells that are rapidly dividing, such as cancer cells."

The DNA double helix was one of the greatest discoveries in science because it laid the foundations for understanding how genetic information is passed from one generation to the next, and how this information controls the biochemistry of the body.

Although scientists had known that DNA could form other unusual structures in the laboratory under artificial conditions, this is the first time that scientists have been able to show that it also forms a quadruple helix within living human cells.

Dr Julie Sharp, the senior science information officer at Cancer Research UK, which helped fund the work, said: "It's been 60 years since its structure was solved but work like this shows us that the story of DNA continues to twist and turn.

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Fresh twist to the DNA story signals major cancer breakthrough

Jan. 20, 2013 In 1953, Cambridge researchers Watson and Crick published a paper describing the interweaving 'double helix' DNA structure -- the chemical code for all life.

Now, in the year of that scientific landmark's 60th Anniversary, Cambridge researchers have published a paper proving that four-stranded 'quadruple helix' DNA structures -- known as G-quadruplexes -- also exist within the human genome. They form in regions of DNA that are rich in the building block guanine, usually abbreviated to 'G'.

The findings mark the culmination of over 10 years investigation by scientists to show these complex structures in vivo -- in living human cells -- working from the hypothetical, through computational modelling to synthetic lab experiments and finally the identification in human cancer cells using fluorescent biomarkers.

The research, published January 20 in Nature Chemistry and funded by Cancer Research UK, goes on to show clear links between concentrations of four-stranded quadruplexes and the process of DNA replication, which is pivotal to cell division and production.

By targeting quadruplexes with synthetic molecules that trap and contain these DNA structures -- preventing cells from replicating their DNA and consequently blocking cell division -- scientists believe it may be possible to halt the runaway cell proliferation at the root of cancer.

"We are seeing links between trapping the quadruplexes with molecules and the ability to stop cells dividing, which is hugely exciting," said Professor Shankar Balasubramanian from the University of Cambridge's Department of Chemistry and Cambridge Research Institute, whose group produced the research.

"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."

Physical studies over the last couple of decades had shown that quadruplex DNA can form in vitro -- in the 'test tube', but the structure was considered to be a curiosity rather than a feature found in nature. The researchers now know for the first time that they actually form in the DNA of human cells.

"This research further highlights the potential for exploiting these unusual DNA structures to beat cancer -- the next part of this pipeline is to figure out how to target them in tumour cells," said Dr Julie Sharp, senior science information manager at Cancer Research UK.

"It's been sixty years since its structure was solved but work like this shows us that the story of DNA continues to twist and turn."

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'Quadruple helix' DNA discovered in human cells

20 January 2013 Last updated at 14:19 ET By Jonathan Amos Science correspondent, BBC News

Cambridge University scientists say they have seen four-stranded DNA at work in human cells for the first time.

The famous "molecule of life", which carries our genetic code, is more familiar to us as a double helix.

But researchers tell the journal Nature Chemistry that the "quadruple helix" is also present in our cells, and in ways that might possibly relate to cancer.

They suggest that control of the structures could provide novel ways to fight the disease.

"The existence of these structures may be loaded when the cell has a certain genotype or a certain dysfunctional state," said Prof Shankar Balasubramanian from Cambridge's department of chemistry.

"We need to prove that; but if that is the case, targeting them with synthetic molecules could be an interesting way of selectively targeting those cells that have this dysfunction," he told BBC News.

It will be exactly 60 years ago in February that James Watson and Francis Crick famously burst into the pub next to their Cambridge laboratory to announce the discovery of the "secret of life".

What they had actually done was describe the way in which two long chemical chains wound up around each other to encode the information cells need to build and maintain our bodies.

Today, the pair's modern counterparts in the university city continue to work on DNA's complexities.

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'Quadruple helix' DNA in humans