Scientists solve longstanding biological mystery of DNA organization

A new technique enables 3-D visualization of chromatin (DNA plus associated proteins) structure and organization within a cell nucleus (purple, bottom left) by painting the chromatin with a metal cast and imaging it with electron microscopy (EM). The middle block shows the captured EM image data, the front block illustrates the chromatin organization from the EM data, and the rear block shows the contour lines of chromatin density from sparse (cyan and green) to dense (orange and red). Credit: Salk Institute

Stretched out, the DNA from all the cells in our body would reach Pluto. So how does each tiny cell pack a two-meter length of DNA into its nucleus, which is just one-thousandth of a millimeter across?


The answer to this daunting biological riddle is central to understanding how the three-dimensional organization of DNA in the nucleus influences our biology, from how our genome orchestrates our cellular activity to how genes are passed from parents to children.

Now, scientists at the Salk Institute and the University of California, San Diego, have for the first time provided an unprecedented view of the 3D of human —the combination of DNA and proteins—in the nucleus of living human cells.

In the tour de force study, described in Science on July 27, 2017, the Salk researchers identified a novel DNA dye that, when paired with advanced microscopy in a combined technology called ChromEMT, allows highly detailed visualization of chromatin structure in cells in the resting and mitotic (dividing) stages. By revealing nuclear chromatin structure in living cells, the work may help rewrite the textbook model of DNA organization and even change how we approach treatments for disease.

“One of the most intractable challenges in biology is to discover the…

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