The nucleus of a cell has something in common with a cardboard box full of kittens: People get so fascinated by the contents that they overlook the container. The nucleus itself is often treated as no more than a featureless membranous bag for holding the vitally dynamic genetic material. Yet in fact it has specialized parts and an internal architecture of its own, and scientists have long speculated that precisely how the DNA positions itself with respect to those parts might matter a great deal.
Now a team of researchers is finding credible evidence that this is true and possibly an important influence on gene expression. Using a new technique based on the genome-editing tool CRISPR, they artificially pinned parts of a cell’s DNA to different regions in the nucleus and observed what happened. The work, published last October in Cell, has begun to yield intriguing insights into how various nuclear neighborhoods may relate to gene expression, as either cause or facilitator.
The 6 feet of DNA intricately bundled within a human cell’s tiny nucleus can look as chaotic as a ball of spaghetti or a tangle of thread. But how that DNA gets situated in three-dimensional space is critical — and not at all random. The degree of packing and folding enables genes to be accessible in the right place at the right time, so that the cell’s machinery can find and decode them, dial their activity up or down, and keep everything working as it should. Those rearrangements also put specific parts of the genome near or far from landmarks within the nucleus. [Continue reading…]