Movie S10.

Progressive spread to entire cell of the presence of the Cry2/CIB1 dimer at the ER surface upon prolonged illumination. HeLa cell expressing ER-CIBN and mCherry-Cry2. Despite the local irradiation of a 3-μm × 10-μm region with 488-nm light pulses of 200 ms every 2 s the activated Cry2 freely diffuses outside of the photoactivation area and binds its interacting partner expressed on the surface of the ER throughout the cell. (Scale bar: 3 μm.)