An ambitious international project to characterize and publish all of the functional elements in the human genome finds that the 80 percent of DNA once thought of a “junk” actually plays a critical role in regulating genes and can also play a part in the onset of disease.

The ENCODE or ENCylopedia Of DNA Elements Project, enlisted the research efforts of some 440 scientists at 32 research institutions around the world. Nature, Genome Biology, and BioMed Central published the results of their work in a series of 30 papers that are being made available for free online. Only 1 percent to 2 percent of DNA encodes for genes. Previously, the vast majority of DNA was thought of as spacers or junk. The research suggests a far more complex view of DNA and how it works and calls for new definitions of genes.

The findings not only creates a new understanding of the role of some 80 percent of DNA once thought to serve no functional role, but provides a new source of potential targets for drugs, and new insight into how genes are regulated and how people become ill.

“During the early debates about the Human Genome Project, researchers had predicted that only a few percent of the human genome sequence encoded proteins, the workhorses of the cell, and that the rest was junk. We now know that this conclusion was wrong,” says Eric Green, director of the National Human Genome Research Institute, a part of the National Institutes of Health. “ENCODE has revealed that most of the human genome is involved in the complex molecular choreography required for converting genetic information into living cells and organisms.”

The researchers found that non-coding DNA plays an active role, acting as switches that modulate genes. This non-coding DNA plays a role in everything from cellular differentiation to the onset of disease.

“We've come a long way,” says Ewan Birney of the European Bioinformatics Institute and lead analysis coordinator for the ENCODE Project. “By carefully piecing together a simply staggering variety of data, we've shown that the human genome is simply alive with switches, turning our genes on and off and controlling when and where proteins are produced.”

The ENCODE Consortium placed its data sets in several free public online databases. These data sets can be accessed through the ENCODE project portal.