Four-strand DNA structure found in cells
2013-01-25 0:00

By Alison Abbott | Nature

Unusual nucleic-acid structure may have role in regulating some genes.

There is no more iconic image in biology than that of DNA’s double-stranded helix, which coils and supercoils on itself to form dense chromosomes.

But a quite different, square-shaped type of DNA structure can easily be created in the laboratory by the folding of synthetic DNA strands rich in guanine, one of the building blocks of DNA. Scientists have long believed that these so-called ’G-quadruplex structures’ may occasionally form in the DNA of living cells. A G-quadruplex comprises four guanines from different places along a G-rich strand held together by a special type of hydrogen bonding to form a compact square structure that interrupts the DNA helix.

In a paper published online today in Nature Chemistry1, researchers led by Shankar Balasubramanian at the University of Cambridge, UK, provide strong evidence that G-quadruplexes do occur in cells — and that these unusual structures may have important biological functions.



A representation of the four-stranded structure (L) with fluorescent markers revealing its presence inside cells (R)


Protecting the chromosome

The protective tips of chromosomal DNA, known as telomeres, are rich in guanine and so are likely candidates for G-quadruplex structures. In fact, studies in cancer cells have shown that small molecules that bind and stabilize G-quadruplex structures cause DNA damage at telomeres, supporting the argument2.

After trawling through human genome data in search of other guanine-rich sequences, some scientists have suggested that quadruplexes could also be created in other areas of the genome involved in regulating genes, particularly some cancer-causing genes.

G-quadruplex visualized

This seems likely to be the case, Balasubramanian and colleagues found. They engineered an antibody that binds tightly and specifically to G-quadruplex structures and does not bind to double-stranded helical DNA. When they incubated the antibody with human cells in culture, they found that it bound to many different sites in the chromosomes, only around a quarter of them in telomeres.

“It’s early days, but if we can map exactly where these G-quadruplex structures pop up in the genome, we may learn how better to control genes or other cellular processes that go awry in diseases like cancer,” he says. “That’s the long-term vision anyway.’’


Article from: nature.com
















Related Articles
Was four-stranded, ‘quadruple helix’ DNA designed or mutated?
Are genes our destiny? ’Hidden’ code in DNA evolves more rapidly than genetic code
DNA directly photographed for the first time
Life on Mars? Scientists hope to find it by decoding Martian DNA - ’We Can Rebuild Them’
Ancient Foreign DNA Found in Modern Human DNA
Far From ‘Junk’, Bits of Mystery DNA Play Crucial Role


Latest News from our Front Page

Increased tax subsidies for politically correct media
2015-03-29 22:08
On Dec 9 last year I translated a random snapshot of the biggest newspaper in Sweden. The headlines alone spoke for themselves. It was, simply put, an orgy of political correctness, obvious attempts at emotional manipulation and general national self-loathing. In other words, a typical Swedish newspaper on any given day. As more and more readers are waking up to the ...
When obeying the law and supporting yourself is racist
2015-03-29 22:56
There is a huge scandal in the municipality of Älmhult in Sweden. It has been revealed that there is a letter that may have been sent from the municipality offices to newly arrived immigrants informing them that the law applies to them and that they’re expected to eventually go off the dole and start pulling their own weight in society. In ...
New political weapon: Threat to unleash immigrant invasion
2015-03-29 22:05
Youtube description: Threatening to bombard a country with illegal immigrants has become quite the bargaining chip in political quarrels, as Polly Boiko explains. Source: youtube.com/RT Editors Note: Notice how the argument is twisted around at the end of the report. The word "Bogeyman" is used. This is a common allusion to a mythical creature. What is mythical about replacement immigration into Europe? ...
Facebook completes first drone flight above UK, Mark Zuckerberg confirms
2015-03-28 3:15
Solar powered drones which provide internet access to rural and remote areas have been trialled in UK for first time by Facebook. They “have a wingspan greater than a Boeing 737 but will weigh less than a car”, according to the social network's chief Mark Zuckerberg. The drones, developed by Somerset-based company Ascenta which Facebook bought last March, will beam down laser-guided ...
300 Young English Girls (and a few Boys) Groomed and Assaulted by Oxfordshire "Gangs," Report Finds
2015-03-28 2:04
Editor's note: This story is a few days old now but the echoes of Rotherham just keeps coming. A few weeks ago there was Halifax, now Britain proudly can add Oxfordshire to their line up of diversity success stories. Below is the story from the telegraph: Serious case review finds failings by police and social services as it identifies hundreds of victims A ...
More News »