CRISPR I-F for the first time used in gene editing
CRISPR toolbox is quite diverse in nature. Bacteria use two classes of CRISPR, which are then divided to six types and at least 22 subtypes.
One of them, CRISPR I-F, belongs to class 1, type I, subtype F. It is used by Yersinia pseudotuberculosis, Pectobacterium atrosepticum, Pseudomonas aeruginosa, as well as Zymomonas mobilis. It’s similar to the first CRISPR system discovered by scientists – CRISPR I-E from E. coli – with the main difference being in PAM defined as 5′-NCC-3′ and in the fusion of Cas2 and Cas3.
A team from Hubei University thoroughly characterized and repurposed CRISPR I-F to perform crucial genetic engineering interventions: nucleotide substitution, gene deletion (knockout), gene replacement, large fragment manipulation. They achieved high efficiency in their organism of choice, Z. mobilis, which is ethanologen with the potential applications in biorefineries.
The method is virtually tailored to that one organism, as it is based on its inner, already existing CRISPR system. Nevertheless, the authors argue:
When compared with the currently routinely used genetic manipulation methods in Z. mobilis, this CRISPR-based toolkit is much simpler, more convenient and time-saving.
Publication: Zheng, Y., Han, J., Liang, W., Li, R., Hu, X., Wang, B., Shen, W., Ma, X., Ma, L., Yi, L. and Yang, S., 2019. Characterization and repurposing of the endogenous Type IF CRISPR-Cas system of Zymomonas mobilis for genome engineering. Doi:10.1093/nar/gkz940.