CRISPRIn 2020 the Nobel prize for chemistry was won by Emmanuelle Charpentier of the Max Planck Unit for the Science of Pathogens in Berlin (Germany) and Jennifer A. Doudna of the University of California in Berkeley (USA). They won the prize for their research on CRISPR-Cas9. CRISPR is a Firure 1: Alfr. Nobel method of removing, adding and medallion replacing DNA to manipulate the genomes of cultured cells, animals, and plants. [1,2] To help you understand CRISPR a little better, five questions about CRISPR and CRISPR -Cas9 will be answered in this article.
What was the research of Charpentier and Doudna? When doing research on bacteria, Charpentier discovered the tracer-RNA (tracrRNA) in bacteria’s ancient immune system. She found out this was part of the CRISPR-Cas system that disarms viruses by cutting their DNA. This finding was unexpected, but she continued working on CRIPSR-Cas in her further research. After the discovery she started collaborating with Doudna, who had been doing research about RNA for a long time. The two bundled their knowledge resulting in a major breakthrough in the scientific world. They succeeded in recreating the bacteria’s CRISPR-Cas system and even making it more easy to use. This resulted in the sharpest tool in gene editing technology. [6]
What is CRISPR-Cas9 and what is CRISPR? CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats.[3] CRISPR-Cas9 has been discovered in the immune system of bacteria, it is an enzyme that cuts double stranded DNA at a targeted location. The CRISPRCas9 complex consists of two main parts: the DNA unwinding and cutting protein called Cas9 and an RNA part functioning as a guide.[4,5] Firure 3: 3D model of the Crispr-Cas9 system
Firure 2: Emmanuelle Charpentier and Jennifer Doudna
By inactivating the Cas9 cutting domain and adding deaminase enzymes the CRISPR complex can perform precise gene editing. The CRISPR complex can edit just one base in the DNA sequence. This precise gene editing disease causes sequences to be deactivated without messing with the rest of the harmless DNA. By adding different proteins to the CRISPR complex gene transcription and silencing can be accelerated.[4] The CRISPR complex can be edited in many other ways. Resulting in CRISPR-systems that can remove, add and replace part of the DNA.
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The CRISPR-Cas system was edited in such a way that it was able to cut double stranded DNA at a targeted place. While the CRISPR-Cas system in the bacteria was only able to cut the DNA of certain viruses and inactivating them, the CRISPR-Cas9 system was able to cut any DNA.[3] This way it is possible to rewrite the genetic code at any place in the DNA.[6] This discovery made the editing of the human genome possible, which is something scientists have been working on for a long time. The tool has contributed to important discoveries in cancer research and research about curing inherited diseases.[6] Besides, the CRISPR-Cas tool can also be used in agricultural research, creating crops that can withstand diseases and extreme weather conditions.[7]
How does the CRISPR-Cas9 system work? The CRISPR-Cas9 system contains of a Cas9 protein containing CIRSPR-RNA (crRNA). The Cas9 has helicases to unwind DNA and nucleases to cut DNA. The CRISPR part contains the information on where the cut should be made. The CRISPR part has crRNA that matches up with the corresponding DNA. In the CRISPR-Cas9 system that was found in the bacteria the crRNA is base paired to the tracrRNA, this holds the crRNA in place. In the CRISPR-Cas9 system created by Doudna and Charpentier the crRNA is attached to tracrRNA, forming a hairpin.[2]
