CRISPR / Cas as a signature antivirus. Part 1

We understand the antiviral immunity of the bacteria CRISPR / Cas, comparing with the signature anti-virus.




CRISPR ( Clustered Regularly Interspaced Short Palindromic Repeats, short palindromic cluster repeats ) - non-coding DNA segments from alternating repeats and spacers, fragments of genomes of viruses parasitizing on this bacterium.
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CRISPR-cassette - a kind of anti-virus database, it stores the orderly data about the threats. Spacers act as signatures: DNA fragments recorded in them recognize viruses and trigger defense mechanisms.

Cell anti-virus protection consists of three stages:

1. Adaptations;
2. Maturation of effector complexes;
3. Immune response.

Adaptation - the acquisition of new spacers. Spacers as signatures cannot be created without interacting with a virus.
When a bacterium is infected, a fragment is cut from the alien genome, by which this virus is recognized in the future.
The protein complex Cas is involved in the adaptation. Like a computer antivirus, it scans the foreign DNA code for “suspicious” sites. Upon finding such, Cas cuts out a fragment of the viral genome and embeds it as a spacer into a CRISPR cassette.

The spacer protects the bacterium until it coincides with the genome of the virus.
The virus accumulates point mutations, losing similarity with the spacer, and this weakens the protection of the bacteria. Polymorphic computer viruses act in a similar way - they change themselves with each new infection, making it difficult to detect.

Spacers already recorded in a CRISPR cassette are useless in the fight against the new virus. CRISPR / Cas, as an anti-virus database, needs to be updated regularly.

Correctly working CRISPR / Cas neutralizes viral infections and prevents the integration of a foreign genome into the cell's genome, such a backdoor at the DNA level.

CRISPR, like the antivirus, is mistaken. CRISPR is characterized by an error like false positive - spacers sometimes coincide with the cell's own genome, then the defense mechanisms work according to the autoimmune scenario, they destroy the DNA of the bacteria.

CRISPR / Cas as a signature antivirus. Part 2

Materials for those interested :
CRISPR systems: immunization of prokaryotes
Genome editing with CRISPR / Cas9
What is CRISPR / Cas9 and how this technology will change medicine
Antivirus software basics