美国加州大学旧金山分校Joseph Bondy-Denomy课题组近期研究发现，噬菌体类核结构可保护自身DNA不受CRISPR核酸酶降解。2019年12月9日，《自然》在线发表了这一成果。

研究人员发现，巨型噬菌体ΦKZ通过构建蛋白核样区域，将其DNA与宿主铜绿假单胞菌的免疫核酸酶分离。ΦKZ对体内靶向DNA的多种免疫机制具有抵抗力，包括CRISPR–Cas3，Cas9，Cas12a的两种亚型以及限制性酶HsdRMS和EcoRI。Cas蛋白和限制性内切酶在整个感染过程中均无法接近噬菌体DNA，但通过对EcoRI在区域内进行重新定位，可以靶向噬菌体并保护宿主细胞。此外，ΦKZ对Cas13a（一种靶向RNA的CRISPR-Cas酶）敏感，可能是由于噬菌体mRNA定位于细胞质。总体而言，研究人员认为，假单胞菌巨型噬菌体通过在其基因组周围组装蛋白质屏障来逃避广谱靶向DNA的核酸酶。

据了解，所有病毒都需要采取策略来抑制或逃避其感染细胞的免疫途径。感染细菌，细菌噬菌体（噬菌体）的病毒必须避免针对核酸的免疫途径（例如CRISPR–Cas和限制性修饰系统）有效复制。

附：英文原文

Title: A bacteriophage nucleus-like compartment shields DNA from CRISPR nucleases

Author: Senn D. Mendoza, Eliza S. Nieweglowska, Sutharsan Govindarajan, Lina M. Leon, Joel D. Berry, Anika Tiwari, Vorrapon Chaikeeratisak, Joe Pogliano, David A. Agard, Joseph Bondy-Denomy

Issue&Volume: 2019-12-09

Abstract: All viruses require strategies to inhibit or evade the immune pathways of cells that they infect. The viruses that infect bacteria, bacteriophages (phages), must avoid immune pathways that target nucleic acids, such as CRISPR–Cas and restriction-modification systems, to replicate efficiently1. Here we show that jumbo phage ΦKZ segregates its DNA from immunity nucleases of its host, Pseudomonas aeruginosa, by constructing a proteinaceous nucleus-like compartment. ΦKZ is resistant to many immunity mechanisms that target DNA in vivo, including two subtypes of CRISPR–Cas3, Cas9, Cas12a and the restriction enzymes HsdRMS and EcoRI. Cas proteins and restriction enzymes are unable to access the phage DNA throughout the infection, but engineering the relocalization of EcoRI inside the compartment enables targeting of the phage and protection of host cells. Moreover, ΦKZ is sensitive to Cas13a—a CRISPR–Cas enzyme that targets RNA—probably owing to phage mRNA localizing to the cytoplasm. Collectively, we propose that Pseudomonas jumbo phages evade a broad spectrum of DNA-targeting nucleases through the assembly of a protein barrier around their genome.

DOI: 10.1038/s41586-019-1786-y

Source: https://www.nature.com/articles/s41586-019-1786-y