As researchers sequenced the genomes of mammals, they came across large regions that didn't seem to contain any protein-coding genes. These "gene deserts" often stretched for thousands of DNA base pairs (called kilobases), and their discovery left researchers arguing about whether they served any function.
One hint that these deserts might be important was the finding that a gene desert on the short arm of chromosome 9 contains some DNA base differences (single nucleotide polymorphisms, or SNPs) associated with coronary artery disease; others were associated with type 2 diabetes.?
The desert runs for almost 200 kilobases. Since there were no real genes nearby, it was unclear exactly how these desert SNPs could manifest themselves as disease. A recent study by Kelly Frazer and colleagues at UCSD, published in Nature, may provide a clue: there are 33 genetic control elements in the desert region.
These control elements are called "enhancers." They are regions of DNA to which proteins bind in a sequence-specific manner; this binding enhances the activity of genes on the same chromosome. An enhancer sequence does not need to be close to the gene it acts upon; it is brought into physical proximity with its target gene through the geometric conformation of the chromosome.
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