They’re all reborn, what’s wrong with being a little more almighty?

Chapter 172 Genetic Scissors
After Zhang Wei's nucleoside modification solved the problem of mRNA breaking through the immune system, the gene editing technology mentioned by Academician Qian became the biggest difficulty in the development of mRNA vaccines.

To say it is difficult does not mean that it cannot be done, but that it is very difficult to do and requires a lot of money and time.

It is not difficult to find viral antigens, but it is indeed difficult to edit the gene sequence corresponding to this antigen separately based on the genetic technology at the time.

For example, the target antigen of the new coronavirus is the spike protein of the virus, so as long as the mRNA sequence of the spike protein is cut out and used as a template, the required mRNA stock solution can be obtained to prepare the corresponding mRNA vaccine.

However, how to cut the mRNA sequence of this spike protein from the virus gene requires a lot of complicated experiments, and whether it can succeed in the end depends on some luck.

Humans discovered restriction endonucleases in the 1970s. This enzyme can recognize specific deoxyribonucleotide sequences and cleave the phosphodiester bond between two deoxyribonucleotides at a specific site. .

In human terms, this enzyme can cut gene fragments.

Since then, humans have had gene editing technology.

However, using endonucleases to cut gene fragments has a fatal disadvantage, that is, the accuracy and efficiency are very low.

The first is that endonucleases are often unable to enter target cells, which means that when I want to cut gene fragments, I cut more than a dozen times, but none of them hit the mark.

Compared with inactivated vaccines, the cost during the development process is definitely advantageous. The technology of virus inactivation has been used for decades, it is very mature, and the cost is completely within the controllable range.

Secondly, in human genes, there is a target for cutting every 500 bases. In other words, you can't cut as long as you want. You need 500 bases to make one cut.

If I can improve the gene editing technology, or develop a new gene editing technology to reduce the research and development costs of mRNA vaccines, can Sinopharm consider investing in the research and development of mRNA vaccines? "

In the mid-1980s, scientists discovered zinc finger proteins, which can be linked to endonucleases, and then developed zinc finger nuclease technology. This technology can achieve targeted cutting of DNA and greatly improve the accuracy.

"You want to develop new gene editing technology?" The three academicians were surprised at the same time.

Finally, there is the price factor. Zinc finger proteins are very expensive. One experiment costs almost 5000 US dollars for zinc finger proteins. Even Americans with deep pockets cannot afford such experiments.

Considering this aspect, Sinopharm's unwillingness to invest in mRNA vaccine technology is also a well-founded decision.

Zhang Wei did not give up, he said: "The currently used gene editing mainly uses zinc finger nuclease technology. Although this technology has been used for twenty years, it does have many shortcomings, which will increase the cost of mRNA vaccine development. .

"Director Meng, don't worry, since I dare to mention this matter, I must have an idea." Zhang Wei said calmly.

If you want a 600-base fragment, you can only cut the 1000-base fragment. The 600-base fragment cannot be cut with one knife.

Secondly, the accuracy of endonuclease is too poor. For example, what I want to cut is this gene fragment, but what I end up cutting is the other end of the gene fragment, or it may be too much or too little.

Considering that Zhang Wei is a talented scholar who was able to publish an article in "Science" at the age of twenty, he might actually have a way to develop new gene editing technology.

But this technology also has great limitations. First of all, zinc finger proteins can affect the recognition and binding of specific nucleotide sequences, which means that you can't cut whatever you want.

Whether it cannot be cut or is not cut accurately, it is a matter that greatly affects efficiency. What's more, the cost of using this method to edit genes is quite high. Unless you have a mine at home, you can't afford it!

Gene editing technology in the past few decades has also relied on restriction endonucleases for research. All gene editing research is trying to improve the accuracy of endonucleases.

The three academicians also felt that Zhang Wei was bragging, but seeing Zhang Wei's calm look, they felt that Zhang Wei might not be innocent.

Until the first decade of the 21st century, humans used this gene editing technology.

If this kind of gene editing technology is used in the development of mRNA vaccines, hundreds of experiments will be carried out and the gene sequence corresponding to the antigen will not be obtained. It is equivalent to spending millions of dollars and not even getting any results. See.

……

Academician Qian explained very clearly, and the people present were all professionals who could understand Sinopharm's concerns.

Meng Heming also quickly advised: "Zhang Wei, gene editing technology cannot be developed through research and development. The existing zinc finger nuclease technology has been used for more than 20 years, and no new technology has emerged. This kind of thing We need to take a long-term approach and don’t make big claims!”

The three academicians looked at each other, and finally it was Academician Qian who asked: "Teacher Zhang Wei, the new idea of ​​gene editing technology you mentioned is to use transcription activators to activate the transcription ability of genes, right? "

"Academician Qian has also read literature on this subject?" Zhang Wei asked with a smile.

"I have read some literature, and there has been research in this area abroad." Academician Qian nodded, and then explained to Director Wang; "There is a kind of Xanthomonas, which is a common pathogenic bacterium in plants and is also a common pathogen in rice white leaves." The main cause of blight.

The Xanthomonas bacterium secretes a protein, a transcription factor, that binds to the host genome and activates its ability to transcribe.

Therefore, some scientists hope to use this transcription ability to activate gene expression to achieve the purpose of gene editing. If this transcription factor can be fused with an endonuclease, it will bring about a revolutionary gene editing technology. "

Director Wang nodded, roughly understanding it, and then he asked: "It shouldn't be easy to implement this project, right?"

"Of course it's not simple. I have only mentioned it in some foreign literature. There may be several teams conducting research in this area with the funding of large foreign companies. There should be no one doing research in this field in China." Academician Qian said.

The next second, everyone looked at Zhang Wei, as if asking, can you really accomplish such a difficult project?

Zhang Wei remained calm and said, "Since I brought it up, I must be sure of it."

"It's true that a newborn is not afraid of tigers. When I was so young, I was like Teacher Zhang Wei. I was full of enterprising spirit! But scientific research cannot be done just by saying that you are sure!" Academician Qian laughed. reminded him.

"How about this? Give me half a year. After half a year, I will ask Director Wang and three academicians to come again to see my results. If the results are indeed worthy of your attention by then, then the mRNA vaccine project , Sinopharm Group should stop refusing," Zhang Wei said.

"Half a year? Is it enough time?" The question this time was from Director Wang. He continued: "Although I am not a scientist, I also know that scientific research cannot be rushed, and experiments also take time.

Teacher Zhang Wei, why not set your time more relaxedly? Anyway, the research and development of a vaccine can easily take more than ten years, so there is no rush. "

"Director Wang, don't worry. The biggest characteristic of me doing scientific research is that I am fast! I said results will be produced in half a year, and results will be produced in half a year! If you don't believe it, I can issue a military order!" Zhang Wei said confidently. "It's not necessary. Our place is not a military camp. Why should we issue a military order?" Director Wang quickly waved his hand.

For this kind of thing, even if a military order is issued, there is no basis for punishment. Sinopharm and Tsingta University are two different units, and they cannot even punish them with three drinks.

Even if Director Wang thought Zhang Wei was bragging, he could only be humane and put on an expectant expression and said, "Then I'm looking forward to Mr. Zhang Wei's research and development results."

……

After seeing off the three academicians, Zhang Wei was called to the office by Meng Heming.

"Are you sure you want to do this project? I just checked some information. The idea of ​​using transcription activators for gene editing is certainly feasible, but it is currently only at the theoretical level." Meng Heming said.

"I did it, so it's not on a theoretical level." Zhang Wei said confidently.

"This project is very difficult!" Meng Heming then reminded.

"How can we trap Sinopharm without releasing a big satellite? We have to let them invest in the research and development of the mRNA vaccine!"

"Actually, there is no need to worry about the research and development of mRNA vaccines. Your paper has just been published. Those pharmaceutical companies are still in the wait-and-see stage. It is normal that no companies will invest."

"Can't you be in a hurry? I want to win the Nobel Prize as soon as possible! Who is the youngest Nobel Prize winner? Lawrence Bragg! He won the Nobel Prize at the age of 25. I am already , and I still can't. Five years!" Zhang Wei said with a smile.

"Lawrence Bragg won the Nobel Prize in 1915! It was still the barbaric age of science, how can it be compared with now!"

Meng Heming paused before continuing: "Besides, you are not allowed to spend money on scientific research? Where do the funds come from? You have to apply to the school! This also takes time. You don't need to push yourself too hard. What kind of military order is there for half a year?"

"Don't you still have a balance for the nucleoside modification project? You were all staring at my balance yesterday, and have you forgotten about it now? I also happened to use this new project to spend all the balance. It saves you time to worry about me!" Zhang Wei responded.

"What you want to do now is gene editing. How many experiments can you do with your little balance? Not to mention other things, such as the existing zinc finger nuclease technology, the cost of one experiment is about US$5000. "

"The transcription activator is secreted by Xanthomonas. Xanthomonas is very common. You can probably collect it from any withered grass leaves on the roadside. The cost is not that high!" Zhang Wei still looked cheerful. expression.

"But endonuclease must be used, right? Other reagents must be used as well? Maybe halfway through the experiment, you will find that you need to use some expensive reagent to proceed!"

"It's okay. I'll apply to the school when the time comes! I went to blackmail the principal, but he had the nerve not to give it? Our Tsinghua University has billions of scientific research funds a year, why should I spend more!" Zhang Wei said carelessly .

"How can you spend billions of dollars a year on you? No one else is doing projects?"

"Can projects done by other people win Nobel Prizes?"

Zhang Wei asked back, and Meng Heming was immediately speechless.

You can win the Nobel Prize, you are awesome!
Zhang Wei still had a smile on his face and said: "Director Meng, let me do it first and give it a try. You know that I am lazy and cowardly. If I can't continue with the subsequent projects, I won't be able to do it." I stopped on my own without you having to ask!

But if I develop a new gene editing technology, it will be a major scientific research achievement, and it will set off a revolution in the entire biological science research. By then, Tsinghua University will make a lot of money just by selling the patents! "

……

The zinc finger nuclease technology, which was developed in the 1980s and has been used ever since, was the first generation of gene editing technology and was also a commonly used technology at the time.

The transcription activator mentioned by Academician Qian is the second generation of gene editing technology. This technology was only developed around 2010.

This technology is also developed based on endonucleases. Due to the cumbersome construction process, the operation is much more difficult than the first-generation technology. Operators with certain experimental skills are required to implement the operation.

Moreover, this second-generation gene editing technology is relatively easy to miss the target. In actual operation, the efficiency does not exceed 25%. In other words, when performing gene editing, only one hit can be achieved for every four cuts.

Such efficiency is actually very worrying when it comes to conducting experiments. This means that the experimenter has to prepare four samples to ensure that one sample can hit the target cell.

If you are less lucky, every shot has a 75% chance of missing the target, which is not impossible! After all, the probability of all four samples missing the target is as high as 31.64%. Eight samples must be prepared to ensure a 90% probability of hitting the target cells.

Compared with the first generation of gene editing technology, this second generation technology is already a revolutionary leap, but this is not Zhang Wei's goal.

When Academician Qian mentioned transcription activators, Zhang Wei also dropped the smoke bomb.

What Zhang Wei wants to do is actually the third generation of gene editing technology.

That is CRISPR-Cas, commonly known as "genetic scissors"!
The first two generations of gene editing technology were all based on endonucleases, but the third generation of gene scissors is different. It is a brand-new gene editing theory.

Within the bacterial genome, there is a repetitive sequence called CRISPR. This sequence is very ancient and can be traced back to the birth of bacteria.

This sequence is the immune weapon used in the fight between bacteria and viruses.

When bacteria detect a viral invasion, CRISPR generates an enzyme called Cas9, forming an immune system called CRISPR-Cas9.

This immune system can directly excise the DNA sequence of the invading virus, thereby resisting viral invasion.

What we normally know about the immune system is that it produces antibodies based on antigens and then exerts an immune effect.

This kind of CRISPR-Cas9 directly targets the DNA of the invader, directly chops the DNA of the invader, and naturally eliminates the invader in the bud.

This is exactly the principle of genetic scissors. Since CRISPR-Cas9 directly cuts DNA sequences, it means that this technology can be used to cut gene fragments.

If I want that gene, just use CRISPR-Cas9 to cut it, and everything will be fine!
(End of this chapter)