Functional metagenomics-guided discovery of potent Cas9 inhibitors in the human microbiome.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31502535.
- Also identified by DOI 10.7554/eLife.46540 and PMC identifier 6739867.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
CRISPR-Cas systems protect bacteria and archaea from phages and other mobile genetic elements, which use small anti-CRISPR (Acr) proteins to overcome CRISPR-Cas immunity. Because Acrs are challenging to identify, their natural diversity and impact on microbial ecosystems are underappreciated. To overcome this discovery bottleneck, we developed a high-throughput functional selection to isolate ten DNA fragments from human oral and fecal metagenomes that inhibit <i>Streptococcus pyogenes</i> Cas9 (SpyCas9) in <i>Escherichia coli</i>. The most potent Acr from this set, AcrIIA11, was recovered from a <i>Lachnospiraceae</i> phage. We found that AcrIIA11 inhibits SpyCas9 in bacteria and in human cells. AcrIIA11 homologs are distributed across diverse bacteria; many distantly-related homologs inhibit both SpyCas9 and a divergent Cas9 from <i>Treponema denticola</i>. We find that AcrIIA11 antagonizes SpyCas9 using a different mechanism than other previously characterized Type II-A Acrs. Our study highlights the power of functional selection to uncover widespread Cas9 inhibitors within diverse microbiomes.
Medical subject headings
- Bacterial Proteins
- CRISPR-Associated Protein 9
- Enzyme Inhibitors
- Microbiota
- Viral Proteins