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Hello, is this DNA?

Weizmann Institute scientists discovered that the DNA coil can be used as a communication wire to transmit messages between distant destinations

Illustration: Yuval Robichak, Weizmann Institute.
Illustration: Yuval Robichak, Weizmann Institute.

The DNA coil can be used as a communication wire to transmit messages between distant destinations - this is the surprising conclusion of the Weizmann Institute of Science scientists who recently found out Because proteins that bind to DNA at a certain point, physically affect a distant point on it, thereby leading to the activation of genes. This type of mechanism has previously been observed in artificial genetic systems, but this is the first time it has been demonstrated in a living organism.

The research group, led by Dr Hagen Hoffman from the Department of Structural and Chemical Biology, first set out to investigate a unique phenomenon that characterizes soil bacteria of the type Bacillus subtilis: A small minority of them can enrich their genome through the absorption of bacterial gene segments scattered in their environment. This ability depends on a protein called ComK, which binds to DNA and thereby activates genes that allow this absorption to take place. However, how this activation occurs has been a mystery until now.

In a new study, led by staff scientist Dr. Gabriel Rosenblum, the scientists examined the DNA of these bacteria using advanced biophysical tools - single-molecule fluorescence resonance energy transfer (single-molecule FRET) and cryogenic electron microscopy - focusing on the two binding sites of the ComK proteins on it.

coiled wire

The researchers discovered that when two ComK molecules bind to one of the sites, a tension is created that is transmitted along the DNA helix, similar to turning a rope at one of its ends, and this occurrence helps the binding of two more ComK molecules at the distant binding site. As soon as all four molecules were bound to the DNA, a threshold was crossed that activates the bacteria's ability to absorb gene segments from its environment.

"We were surprised to discover that DNA not only contains the genetic code, but also acts as a communication wire that transmits information from one protein binding site to another," says Dr. Rosenblum.

To find out exactly how the transfer of information along the DNA is carried out, the researchers introduced various changes in the DNA of the bacteria and examined their consequences. They discovered that in order for the communication to take place, the two binding sites must be at a certain distance from each other and face the same direction on the DNA coil. Violation of these conditions - for example, increasing the distance - weakened the transfer of information; On the other hand, the genetic composition of the segment between the two sites had almost no effect, and when the scientists damaged the integrity of the DNA, the transfer of information stopped altogether - further proof that a physical connection between the two sites is required for the existence of this communication.

Understanding the signaling mechanism through the DNA helix may enable the design of molecular switches that will be used in various applications, for example for the development of transgenic bacteria that will absorb environmental pollution or for the production of enzymes that will be used in the pharmaceutical industry. "Transferring information through DNA is actually a new type of gene control mechanism. This mechanism opens up new ways to develop the 'genetic circuits of the future,'" says Dr. Hoffman.

Dr. Nadav Elad from the Department of Chemical Research Infrastructures also participated in the study; Dr. Haim Rosenberg and Dr. Felix Vigers from the Department of Structural and Chemical Biology; Vykov Jungvirat from the Department of Chemical and Biological Physics.