The Year in CRISPRs - 13

The Year in CRISPRs * CRISPR-Cpf1 May Outsnip CRISPR-Cas9

Gernot Krautberger/Fotolia

(PAM) sequences distinct from those targeted by Cas9, Cpf1 may be able to cut
DNA at locations Cas9 misses. Cpf1 could even be advantaged in targeting certain
genomes, such as those in the malaria parasite or in humans. In addition, Cpf1 cuts
far away from the recognition site, meaning that even if the targeted gene becomes
mutated at the cut site, it can likely still be recut, allowing multiple opportunities for
correct editing to occur.
The third and final feature may be the most important. Essentially, Cpf1 cuts
DNA in a different manner than Cas9. According to the authors of the Cell article,
"Targeted DNA is cleaved as a 5-nt staggered cut distal to a 5′ T-rich PAM."
Whereas Cas9 acts like a conventional pair of scissors, cutting straight across
paired DNA strands, Cpf1 acts more like a pair pinking shears, applying staggered
cuts. When Cpf1 cuts DNA, the cut ends on either DNA strand are offset a bit,
leaving short overhangs. These staggered ends are less vulnerable to mutations
than the "blunt ends" that are left by Cas9. Consequently, CRISPR-Cpf1-altered
genomes may be less prone to fraying during tailoring.
The identification and characterization of Cpf1 was led by Feng Zhang,
who harnessed the CRISPR-Cas9 system for mammalian gene editing in 2013,
independently of George Church at Harvard, who carried out similar work on Cas9.
With respect to the new work, which indicates that Cpf1 is capable of efficient
genome-editing activity in human cells, Zhang said, "We were thrilled to discover
completely different CRISPR enzymes that can be harnessed for advancing research
and human health."
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| GENengnews.com

Cpf1, a newly characterized class II CAS nuclease, is more compact than
Cas9, relies on just one RNA, cuts DNA relatively far from the PAM target
sequence, and results in DNA with staggered, offset ends, not the blunt,
mutation-vulnerable ends left by Cas9.

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The Year in CRISPRs

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