A truncated anti-CRISPR protein prevents spacer acquisition but not interference

Cécile Philippe (1, 2, 3, 4) , Carlee Morency (1, 2, 3, 4) , Pier-Luc Plante (5) , Edwige Zufferey (1, 2, 3, 4) , Rodrigo Achigar (6) , Denise M Tremblay (5) , Geneviève M Rousseau (1, 2, 3, 4) , Adeline Goulet (7) , Sylvain Moineau (1, 2, 3, 4)

1 Département de Biochimie, de Microbiologie et de Bio-informatique, Université Laval
2 Groupe de Recherche en Écologie Buccale (GREB), Faculté de Médecine Dentaire
3 Félix d'Hérelle Reference Center for Bacterial Viruses
4 OENO - Unité de Recherche Œnologie [Villenave d'Ornon]
5 Big Data Research Center
6 UDELAR - Universidad de la República [Montevideo]
7 LISM - Laboratoire d'ingénierie des systèmes macromoléculaires

CRISPR-Cas systems in prokaryotic cells provide an adaptive immunity against invading nucleic acids. For example, phage infection leads to addition of new immunity (spacer acquisition) and DNA cleavage (interference) in the bacterial model species Streptococcus thermophilus, which primarily relies on Cas9-containing CRISPR-Cas systems. Phages can counteract this defense system through mutations in the targeted protospacers or by encoding anti-CRISPR proteins (ACRs) that block Cas9 interference activity. Here, we show that S. thermophilus can block ACR-containing phages when the CRISPR immunity specifically targets the acr gene. This in turn selects for phage mutants carrying a deletion within the acr gene. Remarkably, a truncated acrIIA allele, found in a wild-type virulent streptococcal phage, does not block the interference activity of Cas9 but still prevents the acquisition of new immunities, thereby providing an example of an ACR specifically inhibiting spacer acquisition.

Mots clés: Bacteria; Bacteriophages; Phage biology; Virus–host interactions

Domaines: Sciences du Vivant [q-bio]

Cécile Philippe, Carlee Morency, Pier-Luc Plante, Edwige Zufferey, Rodrigo Achigar, et al.. A truncated anti-CRISPR protein prevents spacer acquisition but not interference. Nature Communications, 2022, 13, ⟨10.1038/s41467-022-30310-x⟩. ⟨hal-03832768⟩