Kamis, 10 Oktober 2013

Puzzling genome: four-stranded DNA found in human cells

G-quadruplex in the model: the four-helix has been demonstrated in human cellsTo enlarge
Jean-Paul Rodriguez
G-quadruplex in the model: the four-helix has been demonstrated in human cells
60 years after the discovery of the building blocks of life researchers have demonstrated for the first time four-stranded DNA in human cells. The strange molecule write them a role in cancer development. So it could be the key to new therapeutic approaches.
Chemists at the University of Cambridge, it is now possible to observe four-stranded DNA molecules in human cells. On task and function of singular molecules, little is known. They are suspected to play an important role in the development of cancer - and therefore could be the key to new therapeutic approaches be. The scientists will now consider whether to switch the molecules and therefore possibly may stop uncontrolled cell growth.

Quite exactly 60 years ago that Francis Crick in a pub near his lab in Cambridge rushed and announced that he had with his colleague James Watson "found the secret of life." This referred to the double-helix structure of DNA, in which two strands twist around each other with genetic information.
Today the descendants of the pioneers of research in Cambridge is still on the molecules of life - and find it ever new. The now discovered quadruple helix call Shankar Balasubramanian and his colleagues also G-quadruplex, as it appears in DNA segments that contain lots of guanine.Guanine is a nucleobase and adjacent adenine, cytosine, and thymine, an important building block of genetic information. In microorganisms such quadruplex structures were detected in the past, but not in humans.
Antibodies recognize the four-helix
Scientists designed antibodies recognizing DNA segments with many quadruplex structures and bind to them. With fluorescence, the team could make the four-stranded DNA regions with the visible and at the same time, determine in which stage of cell division they appear.

Thereby noted chemists that the labeled antibody gleamed always brighter when the cell was in the synthesis phase, in which the DNA is copied before cell division. This observation is of interest in cancer research, as mutated oncogenes in cancer development accelerate the multiplication of DNA and thus contribute to uncontrolled tumor growth.

The researchers hope to break this signal chain with future cancer therapies. In their study in the journal " Nature Chemistry "they could show that the declining number of quadruplex structures have been artificially inhibits DNA amplification. "Our results suggest that quadruplex structures appear rather in genes of rapidly dividing cells such as cancer cells," says Balasubramanian.
The team also observed that an overactive gene with high quadruplex-share sensitive to external influences. May be subject specific cancer genes can be influenced if specially designed molecules to the Vierfachhelices bind them and take as their ability to function.


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