The CRISPR/Cas9 system, a powerful tool for genome engineering and gene regulation, has been thought to be incapable of targeting RNA. This limitation, however, has been overcome by researchers led by CRISPR/Cas9 pioneer Jennifer Doudna, Ph.D., who holds joint appointments at the University of California, Berkeley and Howard Hughes Medical Institute
These researchers reported that they have succeeded in programming CRISPR/Cas9 to recognize and cleave RNA at sequence-specific target sites. This advance, the researchers asserted, could enable direct RNA transcript detection, analysis, and manipulation.
The researchers’ RNA-targeting CRISPR/Cas9 complex, called RCas9, was detailed September 28 in Nature, in an article entitled, “Programmable RNA recognition and cleavage by CRISPR/Cas9.”
“Cas9 binds with high affinity to single-stranded RNA (ssRNA) targets matching the Cas9-associated guide RNA sequence when the PAM is presented in trans as a separate DNA oligonucleotide,” wrote the authors. “Furthermore, PAM-presenting oligonucleotides (PAMmers) stimulate site-specific endonucleolytic cleavage of ssRNA targets, similar to PAM-mediated stimulation of Cas9-catalyzed DNA cleavage.”
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“While RNA interference has proven useful for manipulating gene regulation in certain organisms, there has been a strong motivation to develop an orthogonal nucleic-acid-based RNA-recognition system such as RCas9,” Dr. Doudna said. “The molecular basis for RNA recognition by RCas9 is now clear and requires only the design and synthesis of a matching guide RNA and complementary PAMmer.”
The researchers envision a wide range of potential applications for RCas9. For example, an RCas9 tethered to a protein translation initiation factor and targeted to a specific mRNA could essentially act as a designer translation factor to “up-“ or “down-” regulate protein synthesis from that mRNA.
Read full, original article: CRISPR/Cas9 Can Now Edit RNA, Not Just DNA
