3-D structure of the human genome

A look inside

Scientists have deciphered 3-D structure of the human genome

By Steve Bradt

Harvard Staff Writer

Thursday, October 8, 2009

Image by X. Robert Bao, Leonid A. Mirn, and Maxim Imakaev

A contiguous stretch of DNA chain inside a fractal globule packs into a compact, unknotted structure, making it easy to pack and unpack.

Scientists have deciphered the three-dimensional structure of the human genome, paving the way for new insights into genomic function and expanding our understanding of how cellular DNA folds at scales that dwarf the double helix.

In a paper featured this week on the cover of the journal Science, they describe a new technology called Hi-C and apply it to answer the thorny question of how each of our cells stows some 3 billion base pairs of DNA while maintaining access to functionally crucial segments. The paper comes from a team led by scientists at Harvard University, the Broad Institute of Harvard and MIT, the University of Massachusetts Medical School, and theMassachusetts Institute of Technology (MIT).

“We’ve long known that on a small scale, DNA is a double helix,” says co-first author Erez Lieberman-Aiden, a graduate student in the Harvard-MIT Division of Health Sciences and Technology, a researcher at Harvard’s School of Engineering and Applied Sciences, and a member of the laboratory of Eric Lander at the Broad Institute. “But if the double helix didn’t fold further, the genome in each cell would be two meters long. Scientists have not really understood how the double helix folds to fit into the nucleus of a human cell, which is only about a hundredth of a millimeter in diameter. This new approach enabled us to probe exactly that question.”/.../