Bow-tying DNA

Building on research by CalTech’s Paul W.K. Rothemund, it has been known for considerable time that DNA is folded up to form nanoscale shapes and patterns. The restiform genetic makeup of mammals is folded in bows in order which enables even distant areas to form contacts. It is read by dragging it through cohesin, a ring of proteins, until a stopper is reached. It has been known for some time already that enhancers amplify and activate genes that are positioned far away on the thread of DNA. This can most probably be explained through a precise process of folding back DNA so that enhancers come in contact with the “right” genes. By a commonly accepted hypothesis, this folding back happens as a ring of cohesin molecules surrounds the DNA thread at a random location. It is pulled through the ring until it reaches a “thick” spot that acts as a “stopper.” This thickening is caused by a protein named CTCF that attached itself to the DNA, targeting distant DNA sections for direct contact.

Experiments with mural cells showed that cohesin does indeed move along the DNA thread over long distances with transcription (or “reading” DNA information) acting as an engine. This process is likely powered by RNA polymerase, an enzyme that carries out transcription, probably not least to be able to “read” genetic information in the first place.