Positions of Genes Inside the Cell Nucleus Exert Biological Effects
For decades the cell nucleus has been a black box of biology–scientists have understood little about its structure or the way it operates. But thanks in part to new visualization technologies, biologists have recently begun probing the architecture of the nucleus in real time. And they are discovering that this architecture appears to change as we age or fall ill or as our needs shift. In fact, the structure of nuclear components–chromosomes, RNA, protein complexes and other small bodies–could be as biologically important as the components themselves.
It is not surprising that the nucleus is carefully organized. The human genome’s 3.2 billion DNA base pairs have to be compacted 400,000-fold to fit within the tiny space–yet genes must also interact with one another there and with the machinery that transcribes them into proteins. Nuclear structure has historically been difficult to study because scientists had to rely on electron microscopy or antibody stains, which show cellular components only at single points in time. In the 1990s, however, biologists started using green fluorescent protein to observe nuclear components in living cells in real time, much like a movie. “A picture is worth 1,000 words, and I always like to say a movie is worth one million words,” says David L. Spector, a cell biologist at Cold Spring Harbor Laboratory.
