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Maciamo
24-04-18, 10:27
Scientists discover new DNA structure that's not a double helix (http://bigthink.com/stephen-johnson/study-scientists-identify-new-twisted-knot-dna-structure-in-human-cells)

"In a paper published in Nature Chemistry, researchers from Australia describe the first-ever sighting of a DNA component—called the intercalated motif (i-motif)—within living human cells. The shape of the structure has been likened to a “twisted knot.”

“The i-motif is a four-stranded ‘knot’ of DNA,” said genomicist Marcel Dinger, who co-led the research. “In the knot structure, C [cytosine] letters on the same strand of DNA bind to each other—so this is very different from a double helix, where ‘letters’ on opposite strands recognize each other, and where Cs bind to Gs [guanines].”

To identify the i-motif, which had been previously identified in vitro but never in living cells, the researchers developed antibody fragments dubbed “iMabs” that could recognize and bind to i-motifs in cells. The researchers added fluorescent dyes to the iMabs to make them easy to spot.

“What excited us most is that we could see the green spots—the i-motifs—appearing and disappearing over time, so we know that they are forming, dissolving and forming again,” said Dr. Mahdi Zeraati, the first author of the new paper.

The transient nature of i-motifs, along with the fact that they’re observed near areas of cells that control whether genes get activated, provides clues about their functions.

“We think the coming and going of the i-motifs is a clue to what they do,” said Zeraati. “It seems likely that they are there to help switch genes on or off, and to affect whether a gene is actively read or not.”

Dinger expressed a similar idea to the Australian Financial Review. “It may function as a volume dial in the genome that regulates activity of genes and can impact on the amount of a gene that is expressed in a cell.”"


This is an important discovery for epigenetic research. We already knew that DNA methylation and how tightly histones were wrapped around genes affected the gene expression and activation. This is a third way in which genes could become activated.

Angela
24-04-18, 15:11
Scientists discover new DNA structure that's not a double helix (http://bigthink.com/stephen-johnson/study-scientists-identify-new-twisted-knot-dna-structure-in-human-cells)

"In a paper published in Nature Chemistry, researchers from Australia describe the first-ever sighting of a DNA component—called the intercalated motif (i-motif)—within living human cells. The shape of the structure has been likened to a “twisted knot.”

“The i-motif is a four-stranded ‘knot’ of DNA,” said genomicist Marcel Dinger, who co-led the research. “In the knot structure, C [cytosine] letters on the same strand of DNA bind to each other—so this is very different from a double helix, where ‘letters’ on opposite strands recognize each other, and where Cs bind to Gs [guanines].”

To identify the i-motif, which had been previously identified in vitro but never in living cells, the researchers developed antibody fragments dubbed “iMabs” that could recognize and bind to i-motifs in cells. The researchers added fluorescent dyes to the iMabs to make them easy to spot.

“What excited us most is that we could see the green spots—the i-motifs—appearing and disappearing over time, so we know that they are forming, dissolving and forming again,” said Dr. Mahdi Zeraati, the first author of the new paper.

The transient nature of i-motifs, along with the fact that they’re observed near areas of cells that control whether genes get activated, provides clues about their functions.

“We think the coming and going of the i-motifs is a clue to what they do,” said Zeraati. “It seems likely that they are there to help switch genes on or off, and to affect whether a gene is actively read or not.”

Dinger expressed a similar idea to the Australian Financial Review. “It may function as a volume dial in the genome that regulates activity of genes and can impact on the amount of a gene that is expressed in a cell.”"


This is an important discovery for epigenetic research. We already knew that DNA methylation and how tightly histones were wrapped around genes affected the gene expression and activation. This is a third way in which genes could become activated.

Fascinating stuff. It could explain why there's not a perfect correlation between the presence of certain genes and the effect we expect.

bicicleur
25-04-18, 07:08
is it a temporarily intertwining of 2 double helixes ?