While many people know the CRISPR/Cas9 system as the divisive technique that can edit human genomes, the system was actually derived from bacteria, which uses it to fight off foreign invaders such as viruses, who also use the system. Bacteria typically use the technique to snip and store segments of an invading virus' DNA in order to help them fight it the next time it encounters it, and researchers from the Carnegie Institution for Science have now shown that they can also use it to snip and store segments of RNA.
After biologists first noticed that many bacterial genomes contained repeated segments of "mystery" DNA a few decades ago, they discovered their use years later and very recently used this knowledge to create the CRISPR/Cas9 system, which stands for "clustered regularly interspaced short palindromic repeats," in order to conduct precision gene-editing that is cheaper and more accurate than other alternatives.
There are numerous types of CRISPR/Cas9 systems, and some contain a novel fusion protein consisting of a Cas9 enzyme fused with a reverse transcriptase. Reverse transcriptase's have the ability to read RNA strands and use this information to create a complimentary DNA strand, prompting the researchers to wonder if this could be used to protect against RNA-based invaders.
In the current study, the team worked with the marine bacterium Marinomonas mediterranea and showed that a reverse transcriptase fused with a Cas protein can allow the bacteria to integrate RNA into CRISPR regions and fight off RNA-based invaders.
"The team has demonstrated that this biochemical process can occur in the lab, and based on this information, the CRISPR/Cas system may confer immunity against RNA-based invaders out there in the wild," said Devaki Bhaya, a member of the research team.
"It is gratifying to see how much we can learn from the extraordinary protein diversity that exists in the microbial and viral world, especially when it is combined with rigorous biochemistry," she said, adding that her "colleague, Karl Deisseroth, at Stanford University, summed it up best when he said: 'We need to be supporting the people who are fascinated by pond scum and other obscure topics if we are to eventually treat depression, autism, Parkinson's disease and a host of other complex diseases.'"
The findings were published in the Feb. 26 issue of Science.
