A New Gene-Editing System Called CRISPR-Cas3 Has Been Developed

CRISPR-Cas9 genetic engineering technology enables important advances in treating cancer and other diseases. However, CRISPR-Cas9 also involves many technical problems. In April 2019, a study published in Molecular Cell reported the development of a new gene-editing method called CRISPR-Cas3. The CRISPR-Cas3 method deletes DNA base sequences instead of cutting them.

CRISPR-Cas9 gene-editing systemuses guide RNAto recognize a DNA sequence. Once matching is complete, CRISPR-associated Cas9 proteins position themselves on the target DNA and cut it. The newly developed CRISPR-Cas3 system uses the same mechanism. Instead of cutting target DNA, however, it deletes DNA nucleotides (up to 100 kilobases).

In the research, in the HAP1 (human cell) cell line and human embryonic stem cells, sequences of up to 100 kilobases in targeted DNA were successfully deleted.

CRISPR-Cas3 also has many advantages:

• CRISPR-CAS3 allows genome screening and identification of noncoding gene regions making up 98 percent of the genome. Genetic elements in noncoding regions have important effects on cell differentiation, cancer and protein expression.

Note: If all DNA is compared to space, genes can be thought of as planets and noncoding regions as the ether (gaps) between planets. These regions are also called junk DNA. Although these DNA regions making up %98 of the genome do not encode any gene resulting in protein production, they have important functions.

• CRISPR-Cas3 could successfully delete genes of viruses such as herpes simplex, Epstein-Barr and hepatitis B. In theory, this could provide a complete cure for viral diseases.

Below, the study’s graphical abstract can be seen:

Note: The CRISPR-Cas3 system is also called type 1 CRISPR .

So What Does This Study Mean for Us?

• A gene-editing method more effective than CRISPR-Cas9 has been developed. Instead of cutting DNA, it can precisely delete nucleotides.
• This method could enable effective gene therapies targeting viruses in particular. Viral genes could be eliminated with CRISPR-Cas3.
• It should be emphasized that this method is still being tested at the laboratory stage.