CRISPR systems are prokaryotic adaptive immune systems that use RNA-guided Cas nucleases to recognize and destroy foreign genetic elements. To overcome CRISPR immunity, bacteriophages have evolved diverse families of anti-CRISPR proteins (Acrs). Recently, Lin et al. (2020) described the discovery and characterization of 7 Acr families (AcrVIA1-7) that inhibit type VI-A CRISPR systems. We detail several inconsistencies that question the results reported in the Lin et al. (2020) study. These include inaccurate bioinformatics analyses and bacterial strains that are impossible to construct. Published strains were provided by the authors, but MS2 bacteriophage plaque assays did not support the published results. We also independently tested the Acr sequences described in the original report, in E. coli and mammalian cells, but did not observe anti-Cas13a activity. Taken together, our data and analyses prompt us to question the claim that AcrVIA1-7 reported in Lin et al. are type VI anti-CRISPR proteins.

CRISPR 系统是原核适应性免疫系统，使用 RNA 引导的 Cas 核酸酶来识别和破坏外源遗传元件。为了克服 CRISPR 免疫力，噬菌体进化出了多种抗 CRISPR 蛋白 (Acrs) 家族。最近，林等人。 (2020) 描述了抑制 VI-A 型 CRISPR 系统的 7 个 Acr 家族 (AcrVIA1-7) 的发现和表征。我们详细介绍了对 Lin 等人报告的结果提出质疑的几个不一致之处。 （2020）学习。其中包括不准确的生物信息学分析和无法构建的细菌菌株。已发表的菌株由作者提供，但 MS2 噬菌斑检测不支持已发表的结果。我们还在大肠杆菌和哺乳动物细胞中独立测试了原始报告中描述的 Acr 序列，但没有观察到抗 Cas13a 活性。总而言之，我们的数据和分析促使我们质疑 Lin 等人报告的 AcrVIA1-7 的说法。是 VI 型抗 CRISPR 蛋白。