New York – In a new study released in the journal Cell, Feng Zhang and his team have characterized a new CRISPR enzyme, called Cpf1, that may enable more precise genome editing.

CRISPRs (clustered regularly interspaced short palindromic repeats) are segments of prokaryotic DNA, which forms an immune system that confers resistance to foreign genetic elements. They are known to be used for gene editing by delivering the Cas9 protein and RNA’s into a cell so the organism’s genome can be cut at any desired location.

CRISPR systems help bacteria defend against viral attack. These systems have been adapted for use as genome editing tools in human cells. Credit: Ami Images/Science Photo Library

However, scientists have found that the Cpf1 could lead to a more accurate genome editing since it has different characteristics from Cas9 enzyme, which is commonly used.

According to another study published in the same journal, Cpf1 is a single RNA-guided endonuclease that differs from Cas9 since it cuts the target site to leave sticky ends, and its T-rich proto spacer-adjacent motif (PAM) provides greater flexibility in choosing those target sites.

“This has a dramatic potential to advance genetic engineering,” Eric Lander, the director of the Broad Institute, said in a statement. “The paper not only reveals the function of a previously uncharacterized CRISPR system, but also shows that Cpf1 can be harnessed for human genome editing and has remarkable and powerful features. The Cpf1 system represents a new generation of genome editing technology,” he added.

Inquiring into the matter

There are four main reasons why the use of Cpf1 can improve gene editing.

First of all, Cas9 merges with two RNAs pieces to form a complex able to cut the DNA, while Cpf1 only requires a single RNA. Cpf1 is also smaller than the Cas9 protein, making it easier to deliver into cells and tissues.

Secondly, the Cas9 complex cuts both strands of DNA at the same place, leaving “blunt ends” that, if they rejoin with other blunt ends, could lead to mutations. On the other hand, Cpf1 complex cuts the DNA in two different strands, helping with precise insertion and allowing researchers to integrate a piece of DNA more efficiently and accurately.

Third, even if it results in a mutation, Cpf1’s ability to cut far away from the recognition site allows multiple opportunities for correct editing to occur.

Lastly, the Cpf1 complex recognizes very different PAM sequences from those of Cas9, becoming an advantage in targeting some genomes.

“The unexpected properties of Cpf1 and more precise editing open the door to all sorts of applications, including in cancer research,” noted the Broad’s Levi Garraway, who was not involved in the study, in a statement.

Source: Broad Institute