Loop the Loop, DNA Style
In certain toy racecar tracks, sneaky players can flip a switch, trapping their opponents’ vehicles in a loop of track. Cells employ a less subtle approach: they change the track’s layout. In a study published online in Science, scientists at the European Molecular Biology Laboratory (EMBL) and Oxford University discovered that, by forming or undoing gene loops, cells manipulate the path of the transcription machinery — which reads out instructions from DNA — controlling whether it moves along the genetic material in one direction or two.
Looking throughout the whole genome of yeast cells, the researchers have now found that when genes with ‘one-way’ promoters can’t form loops, transcription from those promoters becomes bi-directional. It seems that with no transcription ‘cars’ trapped in a loop, more are free to move in the opposite direction. And by doing so, they can affect other genes. So by forming or undoing gene loops, cells can control not only what happens to the looping genes themselves, but also adjust the spread of regulation throughout the genome.