A three-dimensional DNA map has been created
Scientists from the University of Cambridge have created the first three-dimensional map of the mammalian genome in a single cell. It shows how all the DNA of a mouse cell is folded inside the cell nucleus. An article with the results of the work was published in the journal Nature (Stevens et al., 3D structures of individual mammalian genomes studied by single-cell Hi-C).
In the first video from the press release of the University of Cambridge Visualizing the genome: researchers create the first 3D structures of active DNA, 20 mouse chromosomes are colored in different colors - VM.
It is known that chromosomes and individual sections of DNA interact with each other through proteins, as a result of which the genome forms dense three-dimensional structures. They do not remain constant, and it depends on them, for example, which genes will be active at the moment.
To establish the spatial organization of the genome, biologists used the Hi-C method. It consists in the fact that formaldehyde is used to fix the contacting DNA sites. The DNA is then cut to form fragments consisting of two protein-linked chains. At the next stage, the chains within the fragment are connected to each other at the ends, and their nucleotide sequence is established.
The researchers analyzed the spatial organization of the genome in eight mouse embryonic stem cells with a single set of chromosomes. DNA has been found to form a number of very dense structures. The researchers built a 3D model of the genome, which demonstrates the location of the contact enhancers with promoters, as well as lamin-associated domains – sections of chromosomes interacting with the nuclear membrane.
In the second video, the regions of chromosomes in which genes are active are colored blue, and the regions that interact with the nuclear lamina (dense fibrillar network inside the nucleus) are colored yellow – VM.
Enhancers are sections of DNA that stimulate the activity of certain genes. To do this, it must contact the gene promoter – a sequence of nucleotides, which is the starting point for the transcription process. The interaction occurs due to the formation of a loop in the DNA, as a result of which the enhancer is in close proximity to the promoter.
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14.03.2017