CRISPR/Cas gene editing system adds new members, Shanghai University of Science and Technology team breaks smallest record

In our traditional impression, "big" and "strong" are always indifferent, but in today's gene editing field, "big" has become a subtraction that bothers researchers, and "small" is the new Goal
.

This week, following the publication of the small Cas13 gene editing system by the team of well-known scholar Professor Zhang Feng, three more small CRISPR/Cas research "groups" from China, South Korea, and the United States went online, frequently rewriting the "minimum" records

▲Three papers in two days focused on the development of a small CRISPR/Cas gene editing system

Why do many researchers focus on the miniaturization of CRISPR? This is essentially determined by the "truck" that transports CRISPR tools into animals-viral vectors
.

One of the most commonly used and most mature viral vectors at present is the AAV virus, which has a capacity of approximately 4.

People are still unable to find a new "truck" that can replace the AAV virus, so the easier solution than "changing the car" is "replacement"-looking for smaller CRISPR systems that can edit mammalian cells
.

Therefore, many teams have begun to work on mining and testing smaller Cas proteins, striving to achieve "no smallest, only smaller"

The three studies that went online this week are all focused on the small nucleases of the Cas12f family.
The Cas proteins of this family generally exhibit a "mini" temperament, with a size of only about 400-700 amino acids, which is smaller than the classic Cas9 Half or more
.

This can free up more space for AAV, so that gene editing tools can bring more "equipment" to battle

The team of Professor Yong-Sam Kim from Korea University of Science and Technology and the team of Professor Lei S.
Qi from Stanford University in the United States both focused on Un1Cas12f1
.

This protein was first reported by the team of Nobel laureate Professor Doudna in 2018 and is 529 amino acids in size

Therefore, on the basis of Professor Doudna's research, the two teams upgraded the original system from different perspectives
.

Professor Qi's team mainly optimized the amino acid composition of the protein and enhanced the interaction with nucleic acids; while Professor Kim streamlined and optimized sgRNA

A team led by Professor Ji Quanjiang of Shanghai University of Science and Technology has studied another new Cas12f family protein—AsCas12f1, which is a nuclease derived from Acidibacillus sulfuroxidans, with a size of only 422 amino acids, which is larger than Un1Cas12f1.
Smaller
.

This protein was first identified by a research team in Lithuania at the beginning of 2020 when it was discovered that it can cut DNA in vitro, but the activity in vivo is unknown

▲The mechanism of CRISPR nuclease AsCas12f1 to cut DNA (picture source: reference [4])

They also found that AsCas12f1 has a unique molecular mechanism, which can cut 3 times on the DNA double-strand (1 time on the targeted strand and 2 times on the non-targeted strand), resulting in asymmetric sticky DNA ends, while most of the other Cas proteins are Cut 2 times
.

"This feature of asymmetric cutting can be used to connect some specially designed sequences

The identification and research of these "mini-version" CRISPR nucleases will provide more sophisticated new tools in the fields of molecular biology, biomedical research and clinical treatment
.

Reference materials:

[1] Zhaowei Wu et al.
, (2021) Programmed genome editing by a miniature CRISPR-Cas12f nuclease.
Nature Chemical Biology Doi: https://doi.
org/10.
1038/s41589-021-00868-6

[2] Do Yon Kim et al.
, (2021) Efficient CRISPR editing with a hypercompact Cas12f1 and engineered guide RNAs delivered by adeno-associated virus.
Nature Biotechnology.
https://doi.
org/10.
1038/s41587-021-01009- z

[3] Xiaoshu Xu et al.
, (2021) Engineered miniature CRISPR-Cas system for mammalian genome regulation and editing.
Molecular Cell Doi: 10.
1016/j.
molcel.
2021.
08.
008

[4] The Ji Quanjiang research group of the School of Matter, Developed a very small CRISPR-Cas12f gene editing tool Retrieved Sep.
3, 2021 from https://