Researchers have discovered a way to program cells to inhibit CRISPR-Cas9 activity. "Anti-CRISPR" proteins had previously been isolated from viruses that infect bacteria, but now University of Toronto and University of Massachusetts Medical School scientists report three families of proteins that turn off CRISPR systems specifically used for gene editing. The work, which appears December 15 in Cell, offers a new strategy to prevent CRISPR-Cas9 technology from making unwanted changes.
"Making CRISPR controllable allows you to have more layers of control on the system and to turn it on or off under certain conditions, such as where it works within a cell or at what point in time," says lead author Alan Davidson, a phage biologist and bacteriologist at the University of Toronto. "The three anti-CRISPR proteins we've isolated seem to bind to different parts of the Cas9, and there are surely more out there."
More information:
Cell, Pawluk et al.: "Naturally occurring off-switches for CRISPR-Cas9" DOI: 10.1016/j.cell.2016.11.017
takyon: Not a dupe of this related story, in case you were wondering.
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UC Berkeley scientists have discovered simple CRISPR systems similar to CRISPR-Cas9—a gene-editing tool that has revolutionized biology—in previously unexplored bacteria that have eluded efforts to grow them in the laboratory.
The new systems are highly compact, befitting their presence in some of the smallest life forms on the planet. If these systems can be re-engineered like CRISPR-Cas9, their small size could make them easier to insert into cells to edit DNA, expanding the gene-editing toolbox available to researchers and physicians.
"These are particularly interesting because the key protein in these CRISPR systems is approximately the same as Cas9, but is not Cas9. It is part of a minimal system that has obvious potential for gene editing," said Jill Banfield, a UC Berkeley professor of earth and planetary sciences and of environmental science, policy and management.
In CRISPR-Cas systems, the Cas protein is the scissors. When targeted to a specific sequence of DNA, the Cas protein binds and severs double-stranded DNA. The new discovery nearly doubles the number of simple and compact CRISPR-Cas systems potentially useful as laboratory and biomedical tools.
"The important thing here is that we found some of these CRISPR systems in a major branch of the bacterial tree, opening the door to a whole new world of microbes that are not cultured in the lab, so we don't really know what they are and what their habits are," said co-author Jennifer Doudna, a UC Berkeley professor of molecular and cell biology and of chemistry and a Howard Hughes Medical Institute investigator. Both Doudna and Banfield are faculty scientists at Lawrence Berkeley National Laboratory.
David Burstein et al. New CRISPR–Cas systems from uncultivated microbes, Nature (2016). DOI: 10.1038/nature21059
(Score: 3, Informative) by Joe on Thursday December 29 2016, @02:46PM
A general off-switch could be useful if the proteins have a long half-life, but the currently available off-switches at the earlier levels (fine-tuning RNA stability or control of transcription with activators and repressors) combined with the ability to change protein stability (at the sequence level) means that these new proteins will have limited usefulness in this function.
The much better use of these proteins would be for lowering off-target edits. These inhibitory proteins could be used to specifically raise the threshold of activity required to successfully edit at non-target regions. Localization of the inhibitors could be controlled with degenerate versions of the on-target gRNA sequence or through protein interaction domains.
- Joe
(Score: 0) by Anonymous Coward on Thursday December 29 2016, @04:17PM
I cliked links and no paper
(Score: 2) by Joe on Thursday December 29 2016, @04:54PM
An AC mentioned that the links didn't work, so I've provided some extra ones below.
Sci-Hub has the pdf, but I'll avoid posting a direct link unless an editor can confirm that it is acceptable.
- Joe
https://www.ncbi.nlm.nih.gov/pubmed/27984730 [nih.gov]
http://www.sciencedirect.com/science/article/pii/S0092867416315896 [sciencedirect.com]
https://en.wikipedia.org/wiki/Sci-Hub [wikipedia.org]
(Score: 0) by Anonymous Coward on Sunday January 08 2017, @01:11AM
thanks Joe!