Hi, I would like to ask simple some questions related to CRISPR-Cas9 that I could not understand by reading some basic articles on it. I am not in that scientific field so my questions might be dull.
1. In nature, the bacteria also needs to make a guide RNA to deactivate the virulent RNA to invade, I guess. In that case, how does the bacteria use the Cas9 protein to obtain the guide RNA? Does it capture a part of invading RNA?
2. Is the CRISPR-cas9 only used to delete the genes or block some parts of genomic sequence to be read? Or does any group make a success to insert genes after cutting the parts of DNA?
3. Is cas9 found in all the bacteria species and only in them? Is any homologous protein found in other organisms?
1, yes, some bacteria contain several invade DNA sequences linked together for it.
2. yes or no, normally, combine the CRISPR-cas9 and Homologous recombination together to insert genes after cutting.
3. not sure.
Article Annotation and classification of CRISPR-Cas systems
Article CRISPR-Cas9/Cas12a biotechnology and application in bacteria
Article Insert, remove or replace: A highly advanced genome editing ...
Hello dear Yeseul Park
When the bacteriophage injects its genome into the host, the bacteria cut the genome and keeps it in the spacer part of its own genome.
When that bacteriophage invades for the second time the bacteria's genome transcripts to mRNA .then some events can happen (depending on the system type) in order to produce cr RNA(CRISPR RNA) :
In type one, for example, cas6e and cas6f cut the mRNA that contains viral genome and produces crRNA with loop this RNA will detect bacteriophage genome in the second attack.
or
In type two tracrRNA (trans-activating CRISPR RNA) binds to the mRNA and the mRNA cuts with cas9. Cr RNA in this type consists of CRISPR+viral genome +tracr RNA.
That's a summary of the system mechanism. There are different types of CRISPR systems with variable functions also there are many types of CAS enzymes that play different roles in the genome editing system. The articles linked above can help you to find your answers.
Hope it was helpful
Good luck
https://international.neb.com/-/media/nebus/files/feature-articles/images/fa_cas9_fig1_cas9invivo.png?h=421&w=600&rev=2ba6bb27fdd2492b9e162cb54486f1da&hash=BFED1B8165C893FED553A9A4DC41A81F
https://www.mdpi.com/antibiotics/antibiotics-08-00018/article_deploy/html/images/antibiotics-08-00018-g001.png
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