Fight against HIV: What is CRISPR-Cas9?

CRISPR-Cas9 is a technology that has hit the headlines in recent years, and that is understandable. Scientists with the ability to modify an organism's DNA are a controversial subject. Last year, a Chinese scientist said he was using this technology for the first time in the world, babies modified to genetic engineering.

But this technology can also have positive effects. Much more recently, US scientists have published an article showing the elimination of HIV in live mice for the first time using two technologies, one of which is CRISPR-Cas9.

But where does CRISPR-Cas9 come from and how can scientists use it to cure genetic diseases?

Understanding the DNA

DNA contains genetic instructions for all living things. It is composed of two strands that wrap around each other and each strand consists of molecules called nucleotides.

The sequence of these nucleotides acts as a code or a blueprint for the formation of proteins, an essential element for all living beings.

Where does CRISPR-Cas9 come from?

Bacteria use CRISPR and Cas9, two different components that work together, to defend themselves.

CRISPR is present in bacteria and other unicellular organisms, but not in humans. This is a term used for nucleotide sequences that are palindromic and repeated. Discovered for the first time in 1987, scientists quickly discovered that this series of repetitive sequences is far from unimportant and plays an important role in the defense of the bacteria against viruses.

To reproduce, a virus must replicate its DNA, but it can not do it alone. It takes an involuntary accomplice. It must divert the machines from a cell, thus opening the way for the destruction of its host. When a virus attacks a bacterium, it inserts fragments of its own DNA into the bacteria. Without knowing it, the protein production machines of the bacteria will now produce viral proteins. Viral proteins are now present in bacteria and they begin to reproduce and assemble, killing bacteria.

But there is a way to stop that. A bacterium that has survived a virus attack sets up a mechanism to save itself the next time another attack occurs. The bacterium chops fragments of viral DNA that have entered the cell and integrated it into its own DNA. These pieces of DNA are then stored between CRISPR repeats.

The bacteria then creates a "most wanted poster" in the form of RNA. This poster is incorporated into the Cas9 protein, which acts as a killer engaged by the bacteria to fight a virus. When Cas9 recognizes that a DNA of an invading virus matches the sequence of "most wanted poster," it cuts out the invading virus's DNA and kills it.

How can CRISPR-Cas9 be used in genome editing?

We all know that scientists are smart, but they have had ideas for editing DNA from organisms that have far fewer cells, bacteria. They copied the whole process we talked about.

They choose the culprit, create the most wanted poster, remove the suspect from Cas9, and then modify the gene so that in case of HIV, the virus can be completely eliminated from the host.

This process can also be applied to diseases not caused by viruses and may exist in our own DNA, such as Huntington's disease and hemophilia.