CRISPR-Cas9 – the hero of the new movie
Scientists have seen how CRISPR-Cas9 cut DNA
CRISPR-Cas9 is a complex of proteins and RNA that is used for precise genome editing. The basis of the complex and method was the immunity system of bacteria, which they use to fight viruses. The system recognizes the sequences of viral nucleic acids and cuts them in strictly defined sections using a spacer – a section of RNA that exactly matches the viral sequence. This ability is being used now to change the genome for research and for medical purposes.
Scientists from Kanazawa State University used an atomic force microscope to observe CRISPR-Cas9. It works like this: a microscopic console is fixed over the object they want to study, which is energized. Forces arise between the console and the sample surface that bend the console. The degree of bending depends on the distance between the surface of the object and the console, and by how much it bends, you can judge the shape of the "relief" of the object.
Scientists applied a DNA sample of 600 base pairs to a mica plate, placed CRISPR-Cas9 in the same place (in different "modifications" – with and without attached RNA) and observed them. From the observation, it was possible to learn several new details: firstly, CRISPR-Cas9 without RNA takes different spatial forms, but after attaching a nucleic acid site, its shape stabilizes. Secondly, CRISPR-Cas9 does not slide along the DNA in search of the right area, as previously assumed, but immediately sits down where it is needed. Thirdly, scientists were able to observe how the structure of the complex changes in the course of work, that is, in the process of cutting DNA.
According to scientists, the observation provided "unprecedented" information about the work of CRISPR-Cas9, and atomic force microscopy showed its potential in observing the work of enzymes that cleave nucleic acids.
The study is described in the journal Nature Communications (Shibata et al., Real-space and real-time dynamics of CRISPR-Cas9 visualized by high-speed atomic force microscopy).
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