Anti-CRISPR proteins encoded by archaeal lytic viruses inhibit subtype I-D immunity.

摘要: Viruses employ a range of strategies to counteract the prokaryotic adaptive immune system, clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR–Cas), including mutational escape physical blocking enzymatic function using anti-CRISPR (Acrs). Acrs have been found in many bacteriophages but so far not archaeal viruses, despite near ubiquity CRISPR–Cas systems archaea. Here, we report functional structural characterization two from lytic rudiviruses, SIRV2 SIRV3. We show that 4 kb deletion genome dramatically reduces infectivity Sulfolobus islandicus LAL14/1 carries subtypes I-A, I-D III-B. Subsequent insertion single gene SIRV3, gp02 (AcrID1), which is conserved deleted fragment, successfully restored infectivity. demonstrate AcrID1 protein inhibits subtype system by interacting directly with Cas10d protein, required for interference stage. Sequence analysis it belongs family compact, dimeric αβ-sandwich characterized extreme pH temperature stability tendency form fibres. identify about 50 homologues four viral families demonstrating broad distribution this group proteins.