耶鲁大学可爱龙课题组的研究开发出了IscB和Cas9转化为RNA引导的RNA编辑器。2025年8月18日，国际知名学术期刊《细胞》发表了这一成果。

该团队报道了一种由IscB设计的超紧凑RNA编辑平台，其活性与Cas13相当或更高，但没有细胞毒性问题。该课题组人员发现Cas9的进化祖先IscB对互补的单链DNA和RNA具有内在的亲和力。当其双链DNA结合活性通过删除其目标邻近基序结构域而关闭时，该活性成为主导。由此产生的R-IscB与Cas13相当或优于Cas13，可以有效地改变人类细胞中的剪接结果，并可以进一步介导反式剪接以纠正mRNA水平上的任何突变。当R-IscB与作用于RNA 2的腺苷脱氨酶（ADAR2）结合时，R-IscB还能在mRNA上驱动有效的A-to-I编辑，并在HNH工程中介导基于切割的mRNA敲低。最后，该团队展示了同样的方法将一些Cas9转化为RNA靶向工具。

据了解，RNA引导的RNA编辑代表了DNA编辑的一个有吸引力的替代方案。然而，流行的工具CRISPR-Cas13具有附带的RNA切割活性，可以在人类细胞中引起不良的细胞毒性。

附：英文原文

Title: Conversion of IscB and Cas9 into RNA-guided RNA editors

Author: Chengtao Xu, Xiaolin Niu, Haifeng Sun, Hao Yan, Weixin Tang, Ailong Ke

Issue&Volume: 2025-08-18

Abstract: RNA-guided RNA editing represents an attractive alternative to DNA editing. However, the prevailing tool, CRISPR-Cas13, has collateral RNA cleavage activity that causes undesirable cytotoxicity in human cells. Here, we report an ultracompact RNA-editing platform engineered from IscB, which has comparable or higher activity than Cas13 but without cytotoxicity concerns. We show that IscB, the evolutionary ancestor of Cas9, has an intrinsic affinity for complementary single-stranded (ss)DNA and RNA. This activity becomes dominant when its double-stranded DNA binding activity is switched off through the deletion of its target-adjacent motif domain. The resulting R-IscB is comparable to or better than Cas13, can efficiently alter splicing outcomes in human cells, and can further mediate trans-splicing to correct any mutation at the mRNA level. R-IscB also drives efficient A-to-I editing on mRNA when fused to adenosine deaminase acting on RNA 2 (ADAR2) and mediates cleavage-based mRNA knockdown upon HNH engineering. Finally, we show that the same approach converts some Cas9s to RNA-targeting tools.

DOI: 10.1016/j.cell.2025.07.032

Source: https://www.cell.com/cell/abstract/S0092-8674(25)00854-2