Zhang Feng: CRISPR-Cas system classification map.

Microbes use a variety of CRISPR-Cas systems to form their immunity, of which class 2 CRISPR systems (especially those based on nuclease Cas9) have become the most popular gene editing tools.
early January, in a new study published in the journal Molen cell, a team led by CRISPR pioneer Zhang Feng discovered two new RNA-targeted CLASS 2 CRISPR systems.
same month, Zhang Feng and two NIH scientists published SnapShot in cell magazine entitled "Class 2 CRISPR-Cas Systems", which provides a detailed generalization of the TYPE 2 CRISPR system (see figure below).
, CRISPR-Cas systems are divided into two categories based on different effect proteins, according to the paper.
Class 1 CRISPR-Cas system utilizes multiple protein effector complexes, while Class 2 CRISPR-Cas systems utilize a single protein effector.
currently, Class 2 CRISPR-Cas systems are divided into 3 types and 9 subsypes.
From a conceptual point of view, there are three main applications: 1) gene editing, including gene knock-out, gene tapping, and mutations;
, what is the information about the classification, mechanism of action, composition and function of class 1 CRISPR-Cas system? On February 23rd three scientists gave answers to these questions in another PaperShot, published in cell magazine, entitled Class 1 CRISPR-Cas Systems.
, based on different family of effect proteins, class 1 CRISPR-Cas systems are divided into three types (I, III, IV) and 12 subsypes (see figure below), according to the paper.
researchers found a class 1 system among different bacteria and ancient bacteria.
example, heat-addicted microorganisms are rich in Type 1 TYPE III CRISPR-Cas systems.
functional aspects, the paper says, in fact, multiple Cas proteins commonly found in Class 1 CRISPR-Cas systems have so far not identified specific functions.
last part of the study, the authors mention anti-CRISPR Protein.
studies have shown that at least some phages can encode multiple anti-CRISPR proteins.
proteins may be used to inhibit CRISPR-Cas systems.
note that in December, Cell published two studies related to anti-CRISPR proteins.
study, entitled "Naturally Dising Off-Switches for CRISPR-Cas9," scientists found three different families of anti-CRISPRs specifically inhibiting the meningococcal CRISPR-Cas9 system.
have confirmed that these anti-CRISPRs can be used as effective inhibitors for gene editing in human cells.
study, entitled "Inhibition of CRISPR-Cas9 with Bacteriophage Proteins," scientists found a variety of inhibitors called anti-CRISPRs in Liste bacteria.
, AcrIIA2 and AcrIIA4 inhibitors were able to block the activity of the streptococcus Cas9 enzyme or ThessyCas9 enzyme.
researchers say these ante-CRISPR sequences are left in the bacterial genome through previous phage infections.
just as CRISPR technology is developed from bacteria's natural antiviral systems, we can also use the anti-CRISPR protein, which uses viruses to evade bacterial defenses, to look for off switches.
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