The term CRISPR stands for clustered regularly interspaced short palindromic repeats. , which translates in Spanish as “clustered and regularly .”
What is CRISPR?
These are DNA sequences that contain a multitude of palindromic segments , that is, sequences that are read in the same way in both directions of the DNA strand.
These palindromic segments are divided by spacer sequences and there is also a “leader” sequence. The set of palindromic sequences, separators and the leader sequence is a CRISPR .
But what is the role of CRISPR?
These sequences are present in 40% of bacterial genomes and 90% of archaea genomes . Archaea are prokaryotic unicellular organisms, that is, they lack a cell nucleus, similar to bacteria and unlike other living beings.
However, here the similarities between bacteria and archaea end, since their metabolic pathways, genomes and biochemistry are similar to eukaryotic organisms (those with a cell nucleus).
Well, the function of CRISPR sequences in these organisms is to defend themselves against viruses. Viruses, at the limit of what separates living and non-living beings, are capable of reproducing thanks to the fact that they parasitize other organisms and use the cellular machinery of their host to replicate their genetic material and assemble new viruses.
This process may include a phase in which the virus integrates its genetic material into the host’s genome, thus spending a variable period of time. This is the case for some human viruses such as influenza , herpes or HIV.
CRISPR works in conjunction with a protein called Cas9, whose name comes from CRISPR associated protein 9. Cas9 is an endonuclease enzyme, which means that it cuts DNA sequences.
An RNA sequence guides Cas9 to a DNA segment complementary to the guide RNA, and Cas9 cuts this DNA sequence. The RNA guide comes transcription (conversion of DNA into RNA) of the spacer sequences present in CRISPR and is complementary to the genetic material of certain viruses.
In this way, if a virus attacks a bacterium or archaea that has a CRISPR sequence with a separator complementary to the genetic material of the virus (which can be DNA or RNA), Cas9 will cut the genetic material, rendering it useless.
Thus, if a virus attacks a bacterium or archaea that has a CRISPR sequence with a separator complementary to the genetic material of the virus (which can be DNA or RNA), Cas9 will cut the genetic material leaving it useless. [/ box]
It is an acquired defensive mechanism that allows the incorporation of genetic sequences of new viruses, being transmitted to the descendants. The usefulness of this defense mechanism against viruses is enormous for bacteria and archaea, but how does it affect other organisms?
Genetic editing thanks to CRISPR
Using a laboratory manipulated CRISPR sequence and the Cas9 enzyme, it is possible to make cuts in any DNA segment whose genetic sequence is known . It is enough to include the complementary sequence to the one that must be cut in a CRISPR separator.
This, on the one hand, allows the inactivation of genes, both of the cell itself and of pathogenic organisms. In other words, CRISPR could be used in humans to eliminate viruses such as HIV , for which there is no cure.
In the case of HIV, and in relation to what was explained above about the viral cycle, current drugs are based on preventing the virus from expressing itself once it has integrated into the DNA of the host cell. But this treatment lasts indefinitely, since the virus is not really eliminated.
There is also the possibility of using other enzymes together, which have the function of joining two cut DNA fragments , allowing the insertion of new genes at points of the genome with known sequences.
The guide RNA locates the point where the union must be made, Cas9 cuts the DNA and the other enzyme inserts the new sequence at the point of the cut, leaving the DNA strand as it was but with a new gene. A genetic manipulation technique with great possibilities.
In both cases, by inactivating genes or introducing new ones, the possibilities offered by CRISPR in fields such as gene therapy for the cure of diseases or the cultivation of transgenic foods are enormous . This new technology has already been called the greatest discovery in genetic engineering so far this century.
Patent war on genetic manipulation
New discoveries in genetic engineering move a lot of money, which is inevitably associated with conflicts of interest and careers on the part of researchers and institutions when it comes to being the first to patent their research.
The CRISPR system was first discovered in 1987 by a group of Japanese researchers led by Yoshizumi Ishino . Years later and independently it was rediscovered by Juan Francisco Mojica, a Spanish microbiologist.
In 2012, doctors Emmanuelle Charpentier, from the University of Umeå, and Jennifer Doudna, from the University of California at Berkeley, published an article in Science describing the possible use of CRISPR for genetic manipulation and subsequently filed the first patent for the discovery. . Later, in 2014, Professor Feng Zhang of the Broad Institute patented the same system but applied to humans.
This generated considerable controversy among academics, since for many it was obvious that the CRISPR mechanism could be applied to humans, so prof. Zhang hadn’t really brought anything new. Subsequent patents based on CRISPR technology are challenged and pending resolution.
Let us hope that this patent war does not harm the development of an exceptional genetic manipulation technique that can be a breakthrough at all levels.