CRISPR might soon partner up with another genome editing tool

Several years back, when scientists discovered that a defense mechanism employed by bacteria to oppose viruses could be turned into a gene-editing tool now known as CRISPR, all things imaginable and unimaginable suddenly became less like something from the realm of science fiction and more of the realm of possibility through science. What if I told you that right now we are making history again by discovering another gene-editing tool that again comes from a defense mechanism of bacteria. They are called retrons and for years scientists have been wondering about their exact function. Retrons are named so because they code for reverse transcriptase, which synthesizes DNA from RNA (Pennisi, 2020). They are a bacterial complex of DNA, RNA, and a protein called an effector. There are many different retrons and one such retron is the Ec48. Their purpose is to defend against bacteriophages, a type of virus that infects bacteria. Once the bacteriophage penetrates the bacterial cell and inhibits the bacteria's first line of defense RecBCD, the retron Ec48 that was guarding RecBCD activates the effector protein, which acts a powerful toxin that destroys the cellular membrane. Essentially, the bacteria is committing suicide before the virus has a chance to replicate (Pennisi, 2020).

Scientists discovered the gene-editing abilities of retrons such as Ec48 that are able to bind and cut regions of a genome, albeit not as efficiently as CRISPR. Nevertheless, where retrons are better is in their ability to introduce new code in the target DNA thanks to its reverse transcriptase, something which CRISPR is not doing so well (Pennisi, 2020). This is why by combining CRISPR with retrons can create such a powerful tool. Their combined strengths creates what scientists like to call CRISPEY, a new genome editing tool that uses CRISPR to bind to a desired location on the genome, CAS9 that acts as a sort of "scissors" to cut the DNA, and then the retron's reverse transcriptase synthesizes the DNA that will replace the section of DNA that was cut out (Pennisi, 2020).

It is now only a matter of time before we know whether CRISPEY will become a thing, and the new genome editing technology to replace CRISPR-Cas9.

Source:

Pennisi, E. (2020, November 11). Microbes' mystery DNA helps defeat viruses-and has genome-editing potential. Retrieved November 19, 2020, from https://www.sciencemag.org/news/2020/11/microbes-mystery-dna-helps-defeat-viruses-and-has-genome-editing-potential