Insights into the inhibition of type I-F CRISPR-Cas system by a multifunctional anti-CRISPR protein AcrIF24

• Published in: Nature communications Vol. 13; no. 1; p. 1931
• Main Authors: Yang, Lingguang, Zhang, Laixing, Yin, Peipei, Ding, Hao, Xiao, Yu, Zeng, Jianwei, Wang, Wenhe, Zhou, Huan, Wang, Qisheng, Zhang, Yi, Chen, Zeliang, Yang, Maojun, Feng, Yue
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 11.04.2022; Nature Publishing Group UK; Nature Portfolio
• Subjects: Adaptive systems; Bacteriophages - genetics; Bacteriophages - metabolism; Binding; CRISPR; CRISPR-Associated Proteins - metabolism; CRISPR-Cas Systems; Deoxyribonucleic acid; Dimerization; DNA; DNA - metabolism; Hybridization; Immune system; Nucleotide sequence; Phages; Proteins; Structural members; Transcription; Viral Proteins - metabolism
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29581-1

CRISPR-Cas systems are prokaryotic adaptive immune systems and phages use anti-CRISPR proteins (Acrs) to counteract these systems. Here, we report the structures of AcrIF24 and its complex with the crRNA-guided surveillance (Csy) complex. The HTH motif of AcrIF24 can bind the Acr promoter region and repress its transcription, suggesting its role as an Aca gene in self-regulation. AcrIF24 forms a homodimer and further induces dimerization of the Csy complex. Apart from blocking the hybridization of target DNA to the crRNA, AcrIF24 also induces the binding of non-sequence-specific dsDNA to the Csy complex, similar to AcrIF9, although this binding seems to play a minor role in AcrIF24 inhibitory capacity. Further structural and biochemical studies of the Csy-AcrIF24-dsDNA complexes and of AcrIF24 mutants reveal that the HTH motif of AcrIF24 and the PAM recognition loop of the Csy complex are structural elements essential for this non-specific dsDNA binding. Moreover, AcrIF24 and AcrIF9 display distinct characteristics in inducing non-specific DNA binding. Together, our findings highlight a multifunctional Acr and suggest potential wide distribution of Acr-induced non-specific DNA binding.