A cutting-edge technique that directly edits proteins in living cells is poised to offer revolutionary insights into how proteins function, behave, and interact within the body. This powerful method, based on the use of self-splicing protein subunits called inteins, allows researchers to insert new chemical groups, unusual amino acids, and even polymers into proteins, all while tracking how these changes affect protein behavior in real time.
Published in Science, this technique could be the protein-editing equivalent of CRISPR, which has transformed genetic research. Though CRISPR revolutionized gene manipulation, the new protein-editing tools, while still in early stages, promise even more precise control over protein functions and locations inside cells. According to Mikko Taipale, a molecular geneticist at the University of Toronto, these tools will vastly improve our ability to probe protein dynamics, offering new perspectives on cell biology.
The Power of Inteins: Nature’s Self-Splicing Proteins
Inteins were first discovered in baker’s yeast in 1990, and since then, researchers have been fascinated by their ability to autonomously excise themselves from proteins. These “Houdini proteins” are known for escaping from the protein structures in which they’re embedded, yet their biological role has remained somewhat mysterious. However, scientists have long seen their potential for editing proteins.
While the idea of using inteins for editing proteins has existed for years, progress has been slow, mainly due to the inefficiency of earlier systems. Now, thanks to new intein designs developed by Tom Muir and colleagues at Princeton University, these systems are much more effective. Their new “protein transposon” editors offer faster and more reliable performance in live cells.
How Protein Editing Works: A “Cut and Paste” Process
The process behind the new protein editors is intricate but clever. Researchers first modify the DNA code of the target protein to include an “acceptor site” for the editing process. This site is flanked by two intein elements. A second protein, the “donor,” is then prepared with the desired modification, such as a new amino acid or chemical group. This donor is also flanked by intein elements. When the target protein and donor align, the inteins “pair up” and cut themselves out, creating a gap in the target protein. The desired modification is then “spliced” into the gap, like a protein-based “cut and paste.”
The process is remarkably fast, with the changes taking less than ten minutes in living cells. This rapid speed opens up new possibilities for studying proteins in real-time, allowing scientists to observe the immediate effects of their edits.
Unlocking New Frontiers in Cell Biology
The potential applications of these protein editors are vast. In addition to marking proteins for tracking, researchers can alter proteins to change their location within cells, modify their function, or force them to interact with other proteins of interest. This level of precision will make it easier to observe how proteins work in living cells and understand their roles in diseases.
The fast-paced nature of these edits allows scientists to monitor protein behavior almost instantly, providing new ways to track protein actions and movements, even as they unfold in real time. For researchers like Muir, the technique offers a whole new level of control and insight.
Challenges and Future Potential
Despite their promise, the new protein editors do have limitations. So far, they have only been effective at exposed or flexible regions of proteins, with highly structured or buried sections proving more difficult to edit. Additionally, the need for an acceptor site limits the editors’ use to modified proteins, and the most efficient method for introducing the donor sequence into cells—electric shock—precludes their use in animal models for now.
However, experts like Taipale are optimistic. “This is the floor, and it’s only going to get better,” he says, hinting that as the technology advances, these tools could become more versatile and easier to apply in broader contexts, including animal studies and potentially human therapies.
As the technology continues to evolve, protein editors are set to become an essential tool for cell biologists and researchers in other fields. They hold the potential to answer longstanding questions about protein function and interaction, and might even offer new approaches for treating diseases that involve faulty proteins.
