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.
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.’’
Hungary’s Orban Bashes Liberal Immigration Policy 2014 08 29 Hungary’s Prime Minister Viktor Orban on Monday lashed out against immigration, setting one of the main policy objectives of his next term in power after winning parliamentary elections in April.
“The goal is to cease immigration whatsoever,” said Hungary’s prime minister. “I think the current liberal immigration policy, which is considered obvious and morally based, is hypocrite,” Mr. Orban said.
At a ...
China’s “Duplitecture” Cities Mimic the World’s Greatest Architectural Hits 2014 08 29 The best knockoffs in the world are in China. There are plenty of fake designer handbags and Rolexes, but China’s knockoffs go way beyond fashion. There are knockoff Apple stores that look so much like the real thing that some employees believe they are working in real Apple stores. And then there are entire knockoff cities. There are Venices with ...
Kiev loses control of Novoazovsk, rebel troops advance in southeast Ukraine 2014 08 29 Kiev’s troops had to leave the eastern Ukrainian city of Novoazovsk to save their lives, said the country’s Security and Defense Council. The authorities admitted that self-defense forces are advancing and leading a counteroffensive in the southeast.
Along with Novoazovsk, Kiev troops have lost control over the villages of Amvrosiivka and Starobeshevo in the Donetsk Region of Eastern Ukraine.
According to Ukraine’s ...
Mohammed is most popular name in Oslo 2014 08 29 For the first time in the capital city’s history, Mohammed is the most common name for boys and men, said a study on Thursday.
Statistics Norway (Statistisk Sentralbyrå - SSB) has counted the population of Oslo and found that Mohammed is the most common male name in Oslo for the first time ever.
Jørgen Ouren of SSB said to NRK: “It is ...
Beaten to Death at McDonald’s 2014 08 29 To the four clean-cut college freshman out on a double date, it had seemed like a typical McDonald’s: spanking clean, well-lighted, and safe. It was in a good neighborhood too, right next to Texas A&M University in College Station -- a campus known for its friendly atmosphere and official down-home greeting: “howdy.”
Shortly after 2 A.M. that Sunday, they pulled into ...