Cell Chem. Biol. 26, 1407–1416 (2019).
Visualizing protein–protein interactions (PPIs) with correlative light and electron microscopy (CLEM) has mostly been restricted to extracellular interactions. To overcome this limitation, Boassa et al. have generated a split-miniSOG reporter. miniSOG has the attractive property of being both fluorescent and able to generate reactive oxygen species upon illumination. These species can then be harnessed to precipitate 3,3′-diaminobenzidine, which reacts with osmium tetroxide to form an EM-visible precipitate. To detect PPIs, the researchers split miniSOG and fused the resulting fragments to the proteins of interest. As the two fragments exhibit low affinity for each other, they only reconstitute in the presence of a PPI, and the reconstitution is reversible when the PPI is no longer present. The researchers illustrate the utility of their split-miniSOG by visualizing the interaction between Fos and Jun in cultured cells, as well as other PPIs, using both light and electron microscopy.
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Vogt, N. Detecting intracellular PPIs with CLEM. Nat Methods 16, 1205 (2019). https://doi.org/10.1038/s41592-019-0681-7