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A Plasmid, a Flash of Light, and a Protein That Snips Itself

Two-minute read


In this study, researchers cloned the gene for PhoCl, a photo-cleavable protein, into plasmids, placing it between different protein components. When those plasmids were delivered into cells, the cells built the PhoCl-containing protein, and light then activates that protein by physically breaking it.


In darkness, PhoCl keeps the attached components covalently connected. But when exposed to violet light near 400 nanometers, it cuts its own protein backbone. Over the next several minutes, its fragments separate—and anything attached to them can be released.


This makes the plasmid less like a simple gene carrier and more like a biological circuit board. Scientists can clone PhoCl between different modules, introduce the plasmid into cells, and then use light to trigger the finished circuit.


The researchers tested several designs. In one plasmid, PhoCl connected a fluorescent protein to a cellular “address label.” Light removed that label, causing the fluorescent protein to move between the nucleus and cytoplasm.


Other plasmids encoded transcription factors and enzymes trapped between inhibitory domains. Once PhoCl was illuminated, those molecular cages fell away. A PhoCl-controlled Gal4 transcription factor increased reporter expression by about 57-fold, while another construct activated Cre recombinase, an enzyme commonly used to rearrange DNA.


The team went even further by cloning PhoCl into a light-controlled protease system. When released, the protease activated an engineered Pannexin-1 ion channel, producing measurable electrical currents and ATP release.


PhoCl is slower than the millisecond switches used in neuroscience, and its cleavage is irreversible. But that is also its strength: a brief flash can create a lasting change without continuous illumination.


We thought this system was wonderfully modular: clone PhoCl into a plasmid, place it between the parts you want to separate, let the cell build the device—and use light to break the protein in two.

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