A study reported the method of locating and modifying single DNA base without random insertion and deletion of genome. This new "base edit" method uses a modified CRISPR / Cas9 protein to make it other two kinds of protein. It is more efficient than the existing method of repairing a single base mutation has been used to culture cells, successfully reversing the single base mutation associated with the diseases including late-onset Alzheimer's disease and breast cancer. The results of recently published in the journal Nature.
Most genetic diseases come from single nucleotide mutation (point mutation). Currently widely focused gene editing technology CRISPR / Cas9 involves cutting two chains of DNA to form a double-strand breaks in the DNA target sequence. However, when a single nucleotide correction for the standard CRISPER / Cas9 method is often inefficient, and frequently introduced randomly inserted into the target location / shear genome, which is mainly the result cell response to DNA double-strand breaks.
In order to improve the efficiency of correction point mutation, while reducing the insertion / deletion frequency, Cambridge, Massachusetts, Harvard University David Liu and colleagues modified Cas9 protein, it no longer cut double-stranded DNA, but still able to bind to the target DNA sequence. By installing bases on Cas9 modifying enzymes (APOBEC1), researchers can directly cytosine (C) is converted into uracil (U), and consistent uracil and thymine (T) base pairing methods. In order for an edited permanent base pairs present in the cell, the researchers used a third protein in normal cells repair DNA to manipulate the process, so that the target C: G base pairs converted to T: A base pairs. Studies have shown that the system can effectively correct the base edit various point mutation associated with human disease in mouse and human cell lines exist, and the introduction of insertions / deletions are extremely low volume.
The other two-year study published in the journal Nature provide new information about Cpf1 enzyme mechanisms and structures. Cpf1 enzyme can be used as a substitute for Cas9 in gene editing CRISPR-mediated. Berlin, Germany Max Planck Society, Institute of Biology infection Emmanuelle Charpentier team has proved the difference between Cpf1 and Cas9. It can perform two activities of RNA processing and DNA cleavage in targeted gene editing, which may open new way of editing and scilenting a specific sequence genome. In another study, China Harbin Institute of Technology research team reported the crystal structure of the RNA Cpf1 attached to the protein and described how the shape changed during the attachment.
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