Finding a needle in a haystack is hard enough. But try to find specific molecules on the needle.
Rice University researchers have achieved something similar with a new genome editing tool that targets the supporting players in a cell nucleus that packs DNA and aids gene expression. Their work opens the door to new cures for cancer and other diseases.
Rice bioengineer Isaac Hilton, postdoctoral researcher and lead author Jing Li and their colleagues programmed a modified CRISPR / Cas9 complex to target specific histones, ubiquitous epigenetic proteins that keep DNA in order, with precision pinpoint.
The open access search appears in Nature Communication.
Histones help regulate many cellular processes. Each nucleosome (the “basic beads on a string” in DNA) contains four that help control the structure and function of our genomes by revealing genes for activation.
“Nucleosomes serve as architectural substrates to insert our DNA into our cells, and can control access to key components of our genomes,” Hilton said.
Like other proteins, histones can be stimulated by phosphorylation, enter a phosphoryl group that controls protein-protein or protein-DNA interactions.
“Histones can exhibit a very diverse spectrum of chemical changes that will be the beacons or regulatory signals and tell which genes to turn, and when, and to what extent to do so,” Hilton said. phosphorylation was one of those mysterious changes, and we aimed to better clarify how human genes can be rapidly converted and removed. “
No other epigenome preparation method has enabled site-specific control of histone phosphorylation, he said. The programmed Rice mechanism, called dCas9-dMSK1, binds deactivated “dCas9” protein and “hyperactive” human histone kinase, an enzyme that catalyzes phosphorylation.
CRISPR / Cas9 typically employs Cas9 guide RNAs and “scissors” to target and cut strands in DNA. The new machine programs implemented dCas9 to target without cutting sequences, instead using the employed dMSK1 enzyme to phosphorylate the targeted histone and turn on nearby genes.
The researchers used dCas9-dMSK1 to discover novel genes and pathways that are essential for drug resistance. Li used it to identify three genes that were previously linked to melanoma drug resistance. “And then she identified seven new genes linked to the fight against melanoma,” Hilton said. “This is an exciting discovery that we are continuing.
“Histone proteins that circulate DNA can have all sorts of chemical signals and combinations,” he said. “As a result we have been given a histone code, and it is one of the Our goals are to work to prove it. “
The Li mechanism also determines how specific histone signals communicate with each other. “It tells us that chemical changes in histones talk to each other, and we can show that it happens at specific places in the human genome,” Li said. “And that’s linked to gene turning on, so this allows us to control them synthetically.”
Li said a long-term goal is to target a range of other histone markers. “It’s a complex story,” she said. “There are many different roles and properties of histones that we want to explore.”
“Getting these technologies to patients is a long process,” said Hilton. “But devices like this are the first step and can pave the way for an understanding. how normal cellular processes unfortunately go awry in human diseases. “
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Magazine Reference:
Li, J., et al. (2021) Programmed human histone phosphorylation and gene activation using CRISPR / Cas9-based chromatin kinase. Nature Communication. doi.org/10.1038/s41467-021-21188-2.