CRISPR tools found in thousands of viruses could boost gene editing

Amazing stuff! CRISPR is everywhere it seems!

"A systematic sweep of viral genomes has revealed a trove of potential CRISPR-based genome-editing tools.

CRISPR–Cas systems are common in the microbial world of bacteria and archaea, where they often help cells to fend off viruses. But an analysis... finds CRISPR–Cas systems in 0.4% of publicly available genome sequences from viruses that can infect these microbes. Researchers think that the viruses use CRISPR–Cas to compete with one another — and potentially to manipulate gene activity in their host to their advantage. ..."

From the highlights and abstract:

"Highlights

• CRISPR pathways encoded in diverse bacteriophage are hypercompact anti-viral systems

• Phage-encoded CRISPR systems encompass all known CRISPR-Cas types

• The Casλ enzyme’s compact structure is capable of plant and human cell genome editing

• These findings reveal a new source of CRISPR-Cas enzymes with value as genome editors

Summary

CRISPR-Cas systems are host-encoded pathways that protect microbes from viral infection using an adaptive RNA-guided mechanism. Using genome-resolved metagenomics, we find that CRISPR systems are also encoded in diverse bacteriophages, where they occur as divergent and hypercompact anti-viral systems. Bacteriophage-encoded CRISPR systems belong to all six known CRISPR-Cas types, though some lack crucial components, suggesting alternate functional roles or host complementation. We describe multiple new Cas9-like proteins and 44 families related to type V CRISPR-Cas systems, including the Casλ RNA-guided nuclease family. Among the most divergent of the new enzymes identified, Casλ recognizes double-stranded DNA using a uniquely structured CRISPR RNA (crRNA). The Casλ-RNA-DNA structure determined by cryoelectron microscopy reveals a compact bilobed architecture capable of inducing genome editing in mammalian, Arabidopsis, and hexaploid wheat cells. These findings reveal a new source of CRISPR-Cas enzymes in phages and highlight their value as genome editors in plant and human cells."

CRISPR tools found in thousands of viruses could boost gene editing Phages probably picked up DNA-cutting systems from microbial hosts, and might use them to fight other viruses.

Diverse virus-encoded CRISPR-Cas systems include streamlined genome editors (open access)

Graphical abstract