As "highlighted" in the June 2009 issue of Discover, M.D. Anderson Cancer Center scientists in Texas have recently engineered a DNA dimmer - allowing them to adjust the intensity at which a cell 'glows' by precisely controlling the production of green fluorescent protein (GFP) within the cell.

By varying the amount of anhydrotetracycline (ATc) added to a population of genetically modified yeast cells, the scientists were able to tweak the levels of GFP produced - thus changing the relative 'glow' of the cells. Doubling the concentration of ATc, for instance, made the cells glow twice as brightly.

Just as engineers rearrange capacitors and resistors to create different electric circuits, researchers can arrange gene promoters and repressors—stretches of DNA that control gene activity—to create gene circuits with different properties. Such circuits have already been used to build a genetic clock and to synthesize cellular machinery that can follow basic logic commands such as AND, OR, and NOR ("not OR").

Biological physicist Gábor Balázsi says his team’s discovery of the genetic dimmer circuit was serendipitous. “We were originally testing for something else,” he says, “so when we found the relationship between ATc and fluorescence, we couldn’t believe it.” Their next step is to investigate whether the circuit works in mammalian cells. If so, it could help researchers understand the effects of genes operating at different intensities and may eventually have applications in therapies for genetic disorders.

Source: http://discovermagazine.com/2009/jun/01-researchers-discover-dna-dimmer