Enzymes Showing Action In Gene-editing

CRISPR, short for CRISPR-Cas9, is a gene-editing tool in which the enzyme Cas9 acts like a pair of molecular scissors, capable of cutting strands of DNA. Once the enzyme makes cuts in DNA at specific sites, insertions and edits can be made, therefore changing the DNA sequence.

The images captured using a technique called cryogenic electron microscopy; or cryo-EM reveal new information about how a gene editing tool called CRISPR-Cas9 works, which may help researchers develop versions of it that operate more efficiently and precisely to alter targeted genes.

Gene-editing enzymes

It is exciting to be able to see at such a high level of detail how Cas9 actually works to cut and edit DNA strands. These images provide us with invaluable information to improve the efficiency of the gene-editing process; so that we can hopefully correct disease-causing DNA mutations more quickly and precisely in the future.

However, to better understand the sequence of events involved in the process; Subramaniam and colleagues used cryo-EM technology to image the Cas9 enzyme at work. The images provide unprecedented glimpses of the stepwise molecular motions that occur in the course of DNA cutting by Cas9; including a snapshot of the cut DNA still attached to the enzyme immediately before release.

Single-turnover enzyme

But one of the main hurdles preventing the development of better gene-editing tools using Cas9; is that we did not have any images of it actually cutting DNA. But now study have a much clearer picture; and we even see how the major domains of the enzyme move during reaction and this may be an important target for modification.

The RNA-guided Cas9 endonuclease from Streptococcus pyogenes is a single-turnover enzyme; that displays a stable product state after double stranded DNA cleavage. The coupled domain motions and interactions between the enzyme and the RNA-DNA hybrid; provide new insights into the mechanism of genome editing by Cas9.