Researchers from theArc Institute in California, led by Patrick Hsu, discovered an RNA-guided system that allows “ modular and programmable DNA insertions, excisions and inversions “. This is a “ precise and powerful tool for recombining and rearranging DNA in a programmable manner “, according to the researchers. However, it is not yet certain whether it works in human cells. This work was published in the journal Nature [1].
A “fundamentally new mechanism”
The publication thus reports the discovery of ” the first DNA recombinase that uses non-coding RNA to specifically select the sequence of target and donor DNA molecules ». Cet « ARN pont » is programmable, allowing the user to specify any desired target genomic sequence and donor DNA molecule to be inserted.
« The RNA bridge system is a fundamentally new mechanism for biological programming “, says Patrick Hsu, lead author of the study, researcher atArc Institute and assistant professor of bioengineering at UC Berkeley.
A “bispecific” guide molecule
The bridge recombination system originates from the elements of insertion sequence 110 (IS110), one of the “ jumping genes » which cut and paste to move inside microbial genomes and between them (see SeekRNA: a “more precise and more flexible” gene editing tool). IS110 elements consist only of a gene encoding the recombinase enzyme and segments of DNA “ supervisors ».
Patrick Hsu’s lab discovered that when the IS110 element detaches from a genome, the ends of the noncoding DNA are brought together to produce an RNA molecule—the “bridge RNA”—that folds into two loops. One loop binds to the IS110 element itself, while the other loop binds to the target DNA where the element will be inserted. The “bridge RNA” is the first example of a guide molecule. bispecific ”, specifying the sequence of target DNA and donor DNA through base pairing interactions.
Each loop of the bridge RNA is independently programmable, allowing researchers to mix and match any target and “donor DNA” sequence of interest. Which means that the system can go “ far beyond its natural role ” which involves inserting the IS110 element itself, instead allowing the insertion of any desirable genetic payload – such as a functional copy of a defective disease-causing gene – into any genomic location.
In this work, the team demonstrated an insertion efficiency of more than 60% of a desired gene in the bacterium E. coli with a specificity of more than 94% in terms of genomic location.
“A universal electrical adapter”
« These programmable bridge RNAs distinguish IS110 from other known recombinases, which lack an RNA component and cannot be programmed. », Explains Nick Perry, from Patrick Hsu’s laboratory. “ It’s like the ARN bridge is a universal power adapter that makes IS110 compatible with any power outlet. »
By continuing exploration and development, the bridging mechanism promises to usher in a new generation of RNA-guided systems, going beyond the DNA and RNA cleavage mechanisms of CRISPR, judge the scientists. Indeed, the bridging recombinase connects the two DNA strands without releasing cut DNA fragments, “ thereby circumventing a key limitation of current genome editing technologies ».
[1] Durrant, M.G., Perry, N.T., Pai, J.J. et al. Bridge RNAs direct programmable recombination of target and donor DNA. Nature 630984–993 (2024). https://doi.org/10.1038/s41586-024-07552-4
Sources : Phys.org, Arc Institute (26/06/2024) ; New Scientist, Michael Le Page (26/06/2024) ; Genetic engineering and biotechnology news, Jonathan D. Grinstein (26/06/2024)
