Guide to Gene Activation
DNA scissors turned into a screwdriver
A team of molecular biologists from Harvard University presented the results of work designed to find out the possibilities of CRISPR/Cas9 technology in a new capacity for it – as a system of artificial regulation of genes (using man-made chemical compounds), and not their editing (direct modification of the DNA structure). The study was published in the journal Nature Methods (Chavez et al., Comparison of Cas9 activators in multiple species).
CRISPR/Cas9 technology recognizes certain regions of genes and cuts them in a specific place, which gives scientists the opportunity to insert the necessary fragment of nucleic acids by editing DNA. When creating this technology, scientists focused on the ability of bacteria to fight viruses with the help of nucleic acids. Viruses introduced their DNA into the cell, and the only chance for the bacteria to escape was its destruction. A special guide RNA recognized a fragment of viral DNA and bound to it, after which the Cas9 protein, like scissors, cut the parasite's genes.
Scientists use CRISPR for different needs. For example, they changed the Cas9 protein, depriving it of the ability to harm DNA. Instead, it was connected to another protein that could activate genes by connecting to enhancers. Enhancers are sections of DNA that can enhance the work of genes if they are combined with a special molecule. The guide RNA recognizes the enhancer, and Cas9 plays the role of an activator. All this allows researchers to precisely control the genes, weakening them or strengthening them. This can be compared to a screwdriver that fits exactly in its place.
But there are a huge number of different Cas9s that differ in their effectiveness and work in different cells in different ways. In order to successfully apply CRISPR/Cas9 technology, it is necessary to know exactly the behavior of its constituent molecules. To find out, the researchers tested a variety of activators on human cells, mice and flies.
Scientists identified three Cas9 activators that had a much stronger effect on the gene than other candidates, and at the same time "hit the target" more often. They were the most versatile, that is, they worked equally well in human and fly cells. According to the researchers, the found leading three molecules can be made the basis for further improvements.
CRISPR is a DNA fragment that combines repeating parts – short palindromic repeats – and spacers. Spacers differ from each other in nucleotide sequences and are located between repeats. They are parts of DNA borrowed from viruses or parasitic bacteria and are responsible for recognizing foreign genetic material similar to them.
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25.05.2016