Bacteria’s strategy to stop viruses reveals clues about human immunity

*This content was produced by experts from the Weizmann Institute of Science, one of the world’s leading centers for multidisciplinary basic research in the natural and exact sciences, located in Rehovot, Israel.

the Phages, Viruses that attack bacteria, Owns Head and tail. The head contains the phage’s genetic material, and the tail is used to identify a potential host, a bacterial cell into which you can inject this material. Once the injection is complete, the phages hijack the bacteria’s cellular machinery and force it to produce new copies of itself, eventually causing the cell to explode and Infect other bacteria in the colony..

In a new study who published in nature Researchers in Weizmann Institute of Science It reveals a bacterial immune system that thwarts phages’ plans by attaching a small protein molecule to their tail. The components of this new immune system are similar in structure to those of Human immune mechanism, It could help reveal how this mechanism works and How our immune system evolved.

First mechanisms Counter defense Bacteria were discovered in the 1960s, but until recently only a few were known. The most famous of them is CRISPR-Cas9, whose discovery was a revolution in Gene editingHowever, in recent years there has been a wave of new findings in this field that have led to the discovery of More than 150 new bacterial immune systems With different working methods. Many of these systems have been identified using the method developed by Prof. Rotem Soreq, The follower Department of Molecular Genetics By Weizmann.

Sorek’s method is based on a surprisingly simple principle: genes involved in bacterial immune mechanisms tend to cluster in the bacterial genome, in regions known as “Defense islands”. Therefore, researchers can discover new immune systems by examining Genes of unknown function which are located near known defensive islands. “In many of our studies, we identified components of bacterial immune systems that were familiar to us from well-studied human immune mechanisms,” explains Sorick. “This suggests that The evolutionary source of much of our innate immune system comes from bacteria.“Our new study further supports this idea.”

In the 1970s, scientists discovered a cellular control system that can change the structure and function of proteins, as well as their lifespan, by attaching a small protein called ubiquitin to them. Since the discovery ubiquitin (Which professors Aaron Ciechanover, Avram Hershko, and Irwin Rose received the award. Nobel Prize in Chemistry 2004), and other scientists have uncovered many similar systems, in which Enzymes bind many small proteins to the target protein, thus modifying its fate..

In the new study, researchers led by Dr. Jens Hoer, From the Sorek lab, they discovered a new bacterial immune system that contains a ubiquitin-like protein With a structure similar to that of ISG15It is one of the most mysterious proteins in the human immune system. ISG15 plays a role in defense against various viruses, such as Influenza and HIV, But it’s not entirely clear how it accomplishes its mission.

Hoare and his colleagues found that, unlike other bacterial immune systems, the system they discovered did not prevent viruses from hijacking the cell and creating duplicates of themselves: The bacteria that encode this immune system, Once infected, they died and produced new viral offspring.But these viruses were “SterileThat is, they cannot infect other bacteria, leading researchers to conclude that the new immune system is capable of doing so. Prevent the virus from spreading in some way. to other cells in the colony.

To understand how Replicated viruses lose their ability to infect other cells. And what role does the new bacterial immune system play in this? The Soreq research team collaborated with the Soreq research team Dr. Sharon Wolf, Head of the Electron Microscopy Unit in the Weizmann Chemical Research Support Division. The researchers labeled the ubiquitin-like protein at the heart of the new immune system with gold particles that can be clearly seen under a microscope.

When they looked at the pictures duplicate gaps, They were amazed: The tagged protein was located at the end of the viral tail, preventing the phages from using their tails to locate and infect new bacterial cells. The researchers believe that this new immune system is able to recognize the three-dimensional structure of the viral tail, allowing the system to work effectively against a wide range of phages, as long as they have tails with similar structures.

“We hope that our discovery in bacteria will inspire researchers studying the human immune system.” Study whether a similar principle applies to the human immunoglobulin ISG15. “Viruses that attack humans may not have tails, but human defenses may also work by changing the virus’s main structural protein,” says Sorek. “The immune system we discovered in this study is just one of many systems that contain ubiquitin-like proteins that we have identified in bacterial genomes. Now, it remains to be seen how these other systems fight their ancient enemies, viruses.”