A team of international scientists, headed by Professor Peter Fineran from the University of Otago and Dr. Rafael Pinilla-Redondo from the University of Copenhagen, recently published their findings in Nature about a novel method employed by viruses to inhibit the bacterial CRISPR-Cas immune systems.
The study's co-author, Dr. David Mayo-Muñoz from the Phage-host interactions (Phi) laboratory in Otago’s Department of Microbiology and Immunology, emphasized the potential implications of this research. “The discovery is exciting for the scientific community because it provides a greater understanding of how CRISPR-Cas defenses can be stopped,” he commented.
Bacteria use CRISPR-Cas as a defense system against invading bacterial viruses or phages. This defense mechanism involves integrating fragments of phage DNA into the bacterium's genome. Essentially, the bacteria create a "memory bank" of prior phage infections, which functions similarly to a mugshot collection, helping bacteria recognize and target specific phages during subsequent invasions.
Dr. Mayo-Muñoz explained the process: “If a virus comes in, part of its DNA is added to the memory bank, and then turned from DNA to RNA in the process. Each RNA acts like a guide so the CRISPR-Cas system can correctly identify and destroy the invading phage. Each addition to the memory bank is divided by a CRISPR repeat sequence, which stacks up like bookends between each phage sequence.”
“The interesting thing is that phages have evolved different ways to overcome these defense systems—it’s like an evolutionary arms race. Bacteria have CRISPR-Cas so the phages have developed anti-CRISPRs, which enables them to block the immune complexes of the bacteria.”
“What we’ve discovered is a whole new way that phages can stop CRISPR-Cas systems,” said Mayo-Muñoz.
Earlier studies noted the presence of CRISPR repeat sequences in some phage genomes. Building on this observation, the joint Otago-Copenhagen research team showed that phages introduce these RNA repeats into bacteria to counteract CRISPR-Cas.
Commenting on this, Professor Fineran stated, “Phages have components of bacterial CRISPR-Cas systems in their own genomes. They use these as molecular mimics for their own benefit to silence the immune system of bacteria and allow phage replication.”
The researchers further observed that when a phage introduces RNA repeats onto the CRISPR-Cas proteins, not all the appropriate proteins are incorporated, resulting in an inactive complex. “This molecular mimic ruins the defenses of the bacteria and the function of the system; it’s basically a decoy,” Fineran elaborated.
Given the rising interest in the potential of CRISPR-Cas to edit genomes with precision—evidenced by a recent Nobel Prize in Chemistry acknowledgment—anti-CRISPRs offer an intriguing avenue for refining this technology.
Dr. Mayo-Muñoz pointed out, “To harness the potential of CRISPR-Cas technologies, it is important to be able to control it, turn it on and off, and tune it, improving its accuracy and therapeutic benefit. Our discovery is the first evidence of an RNA anti-CRISPR, which has a shorter genetic sequence than previously discovered protein anti-CRISPRs, and since they are based on known CRISPR repeat sequences, we have the possibility to design RNA anti-CRISPRs for all CRISPR-Cas systems and their specific applications.”
With the promise of CRISPR-Cas being employed for gene therapies to rectify mutated genes causing diseases, the incorporation of anti-CRISPRs is paramount for safe applications. Additionally, as phages offer an antimicrobial solution against harmful bacteria, they present an alternative to traditional antibiotics.
Professor Fineran concluded, “We are excited to be able to provide a whole new insight into how phages battle with their bacterial hosts. We hope that these RNA anti-CRISPRs will provide a new approach to help control CRISPR-Cas technologies.”
The study's co-author, Dr. David Mayo-Muñoz from the Phage-host interactions (Phi) laboratory in Otago’s Department of Microbiology and Immunology, emphasized the potential implications of this research. “The discovery is exciting for the scientific community because it provides a greater understanding of how CRISPR-Cas defenses can be stopped,” he commented.
Bacteria use CRISPR-Cas as a defense system against invading bacterial viruses or phages. This defense mechanism involves integrating fragments of phage DNA into the bacterium's genome. Essentially, the bacteria create a "memory bank" of prior phage infections, which functions similarly to a mugshot collection, helping bacteria recognize and target specific phages during subsequent invasions.
Dr. Mayo-Muñoz explained the process: “If a virus comes in, part of its DNA is added to the memory bank, and then turned from DNA to RNA in the process. Each RNA acts like a guide so the CRISPR-Cas system can correctly identify and destroy the invading phage. Each addition to the memory bank is divided by a CRISPR repeat sequence, which stacks up like bookends between each phage sequence.”
“The interesting thing is that phages have evolved different ways to overcome these defense systems—it’s like an evolutionary arms race. Bacteria have CRISPR-Cas so the phages have developed anti-CRISPRs, which enables them to block the immune complexes of the bacteria.”
“What we’ve discovered is a whole new way that phages can stop CRISPR-Cas systems,” said Mayo-Muñoz.
Earlier studies noted the presence of CRISPR repeat sequences in some phage genomes. Building on this observation, the joint Otago-Copenhagen research team showed that phages introduce these RNA repeats into bacteria to counteract CRISPR-Cas.
Commenting on this, Professor Fineran stated, “Phages have components of bacterial CRISPR-Cas systems in their own genomes. They use these as molecular mimics for their own benefit to silence the immune system of bacteria and allow phage replication.”
The researchers further observed that when a phage introduces RNA repeats onto the CRISPR-Cas proteins, not all the appropriate proteins are incorporated, resulting in an inactive complex. “This molecular mimic ruins the defenses of the bacteria and the function of the system; it’s basically a decoy,” Fineran elaborated.
Given the rising interest in the potential of CRISPR-Cas to edit genomes with precision—evidenced by a recent Nobel Prize in Chemistry acknowledgment—anti-CRISPRs offer an intriguing avenue for refining this technology.
Dr. Mayo-Muñoz pointed out, “To harness the potential of CRISPR-Cas technologies, it is important to be able to control it, turn it on and off, and tune it, improving its accuracy and therapeutic benefit. Our discovery is the first evidence of an RNA anti-CRISPR, which has a shorter genetic sequence than previously discovered protein anti-CRISPRs, and since they are based on known CRISPR repeat sequences, we have the possibility to design RNA anti-CRISPRs for all CRISPR-Cas systems and their specific applications.”
With the promise of CRISPR-Cas being employed for gene therapies to rectify mutated genes causing diseases, the incorporation of anti-CRISPRs is paramount for safe applications. Additionally, as phages offer an antimicrobial solution against harmful bacteria, they present an alternative to traditional antibiotics.
Professor Fineran concluded, “We are excited to be able to provide a whole new insight into how phages battle with their bacterial hosts. We hope that these RNA anti-CRISPRs will provide a new approach to help control CRISPR-Cas technologies.”