PIXABAY, PUBLICDOMAINPICTURESThe CRISPR/Cas9 system is already a widely used precision gene-editing tool, but a group of researchers from the Broad Institute of MIT and Harvard have engineered the Cas9 protein to make it even more efficient. By altering three of Cas9’s amino acids, researchers were able to significantly reduce the occurrence of off-target gene edits. The results were published yesterday (December 1) in Science.
“For therapeutic applications, we all want to proceed with maximum caution to make sure we’re not modifying the genome at undesired locations,” David Liu, a chemical biologist at Harvard University who was not involved with the work, told Nature.
Even with Cas9’s precision, the protein still sometimes made mistakes between the RNA that guides it and the DNA that it actually binds. The three edited amino acids, each with a positive ion charge, normally help Cas9 bind to DNA—which is negatively charged. Replacing these amino acids with alanine, which is neutral, hindered Cas9’s ability to bind off-target DNA sites without significantly affecting the correct edits. “It’s a matter of tempering the excess ‘enthusiasm’ of Cas9, so that it grudgingly accepts on-target sequences and nothing else,” ...
