Weizmann Institute of Science scientists have created the smallest artificial genetic circuit ever. The new development based on a single DNA molecule is expected to promote the next generation of nanobiotechnological applications
Weizmann Institute of Science scientists recently observed a protein born outside the cell from a single DNA molecule. It was an unprecedented event, but what followed was no less groundbreaking: the insights from the observation allowed them to plan the The smallest artificial genetic circle ever - A scientific achievement that is expected to help create artificial cells and miniaturized biological devices. "We discovered a very clever design principle in nature, and we adopted it to create an independent genetic circuit based on a single DNA molecule," says Dr. Ferdinand Grace, who led the research in Prof. Roy Bar-Ziv in the chemical and biological physics department of the institute.
Like an electrical circuit consisting of a collection of components that work together to perform a certain action, for example turning on or off a light bulb, a "genetic circuit" is an image of a network of cellular components - genes, promoters and control proteins - that work together to carry out the process of gene expression and other functions. Just as an electrical circuit is an independent basic unit in more complex electronic devices, the genetic circuit is also an independent unit that may form the basis for the development of artificial biological machines that will be used in a variety of medical and industrial applications.
No idleness at sixty
Artificial cells are a major area of research in Prof. Bar-Ziv's laboratory. As part of his post-doctoral research, Dr. Grace examined various aspects of gene expression - that is, the production of proteins based on the "prescriptions" encoded in the genes - in the framework of artificial cells. To this end, he engineered DNA molecules extracted from E.coli bacteria and created a basic genetic circuit from them - a gene that encodes a control protein that serves as an ON button and in turn activates another target gene; A fluorescent tag is attached to the target gene that lights up when the gene is expressed and allows you to receive an indication of the completion of the process. First, Dr. Grace inserted about 10 genetically engineered DNA molecules into an artificial cell. In a living cell as in an artificial cell, hundreds or thousands of copies of control proteins are often required to ensure that the encounter with the target gene actually occurs. On the other hand, the 10 molecules floating in the ocean of cellular fluid like the remains of a shipwreck, are not supposed to reach a safe harbor easily and quickly. However, to the scientists' surprise, the fluorescent tag turned on almost immediately. How did so few control proteins find their way into DNA so quickly?
The next step was even more surprising: even when Dr. Grace used a single DNA molecule, the fluorescent tag turned on very quickly. A possible explanation for this is that the control protein does not float in the cell fluid but remains temporarily attached to the DNA. In fact, previous studies have already indicated such a possibility in bacteria such as E.coli, but this hypothesis could not be confirmed with the existing technology. The reason: Protein production is a fast process that takes less than a minute, while fluorescent tags often need a few minutes to light up.
In collaboration with colleagues from Germany, Dr. Grace developed a new type of tag that can be lit in a few tens of seconds. He then built a device that allowed him to use the new tag to view individual molecules under a microscope. This is how he and his colleagues were able to observe a newly born control protein and see that it indeed lingers over the DNA molecule like a baby attached to its mother by the umbilical cord. "I was fascinated to find out how evolution created such an economical design," says Dr. Grace, adding that the findings experimentally confirmed the hypothesis of the existence of a genetic planning principle, which until then was only a theory.
Later, the scientists used this principle to engineer an entire genetic circuit on a single DNA molecule. In addition to an ON switch, they also added an OFF switch, and both switches were programmed to remain connected to the DNA until their work was done. In the future, based on the same design principle, it will be possible to add more and more functions and capabilities to artificial genetic circuits.
"We showed that a single DNA molecule can serve as the basis for an entire genetic circuit," says Prof. Bar-Ziv. "This means that we can see the DNA molecule as an independent unit that does not have to be confined within a membrane, but can function in any cell volume, and thus be used as an independent miniaturized device in many future applications, from biological calculations to medical diagnosis and treatment."
Dr. Shirley Dauba from Prof. Bar-Ziv's laboratory also participated in the study; Dr. Nicholas Lardon from the Max Planck Institute for Medical Research in Heidelberg, Germany; Dr. Leonie Schutz and Prof. Elmer Weinhold from Aachen University, Germany; Dr. Yoav Barak from the Department of Chemical Research Infrastructures of the Weizmann Institute; and Prof. Vincent Noiro from the University of Minnesota, Minneapolis, Minnesota, USA.
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