On 13th October, a paper entitled"Harnessing Type I and Type III CRISPR-Cas systerms for genome editing"was published online in Oxford Journals: Nucleic Acids Research (IF:9.112). As the latest findings of CRISPR system research and application, it was the joint effort of the Archaea Molecular Biology Research Group from the State Key Laboratory of Agricultural Microbiology at HZAU. It first proposed a method of using Type I and Type III CRISPR-Cas systerms to conduct genome editing. Doctoral student Li Yingjun from College of Life Science and Technology is the first author, and Prof. She Qunxin and Prof. Liang Yunxiang are corresponding authors.
CRISPR-Cas system, as an acquired immune system of procaryotic organism by defending exogenous invading nucleic acid, widely exists in about 90% archaea and 40% bacteria. CRISPR-Cas systems are currently classified into three main groups: Type I, Type II and Type III. Type II only needs a protein of Cas9, a crRNA and trans-acting RNA to perform interfering activity, thus it can be developed to be the tool for genome editing. However, CRISPR/Cas9 system still has some limitations, such as complex procedures, off-target effect and application limits in extremophiles. The genome editing method that uses Type I and Type III systems in this study is based on the procaryotic organism’s own CRISPR system. First, it only needs to construct and editing plasmid which concurrently carries artificial CRISPR array and DONOR DNA. Second, when the editing plasmid is transformed to host cell, crRNAs provided by artificial CRISPR array and Cas proteins supplied by CRISPR system will form a ribonucleoprotein complex (crRNP), which will exert DNA interference to the targeted gene. Finally, the genome editing can be achieved through the homologous recombination of DONOR DNA and targeted gene. The editing types include deletion, insertion and mutation.
The advantages of this method lie in: the wide range of applied hosts; participation of homologous recombination which avoids off-target effect and strengthens the editing specificity; higher editing efficiency and high screening rate of the positive; simple procedure and short operation period.
They have applied for a new patent for the genome editing method for procaryotic organism using endogenous CRISPR-Cas system”.
(By SHI Yafen)
