Project members also catalogued sequences that mark areas where DNA unwinds from the round histone proteins that maintain the shape of chromosomes, allowing the cell's transcription machinery to activate genes in those areas. They discovered some potentially unwound areas that are far from promoters and may therefore play some other role, Birney says.
The consortium found that 5 percent of the studied sequence has been conserved among 23 mammals, suggesting that it plays an important enough role for evolution to preserve while species have evolved. But of all the new ENCODE sequences identified as potentially important, only half fall into the conserved group.
These unconserved sequences may be "bystanders," Birney says—consequences of the genome's other functions—that neither help nor hurt cells and may have provided fodder for past evolution.
They could also simply maintain a useful DNA structure or spacing between pieces of DNA regardless of their particular sequence, says genomics researcher T. Ryan Gregory of the University of Guelph in Ontario, who was not part of the consortium.
"The biological insights are mainly incremental at this point," says genome biologist George Weinstock of the Baylor College of Medicine in Houston, which he says is to be expected of such a pilot study. "This is a 'community resource' project, like a genome project, that makes lots of new data available to the community, who then dig into it and mine it for discoveries."
Gregory says the results, although still cryptic, do hint at new functions and a more complicated genome. "This study shows us how far we are from a comprehensive understanding of the human genome."