Figure 3.

Cell‐cycle control with blue light. a) General mechanism of cell‐cycle arrest induced by photoactivated MG132‐Cage. Blue‐light irradiation releases MG132, which inhibits the proteasome leading to arrest in metaphase. For depiction of the human proteasome crystallographic data (PDB code 5GJR) from Ref. [28] were used. b) Key experimental setups to quantify blue‐light‐induced metaphase arrest. c) Confocal microscopy images of HeLa cells incubated with MG132‐Cage and either maintained in the dark (left) or exposed for 10 min to 405 nm light (right). Cells were stained for DNA (blue), F‐actin (green), and α‐tubulin (orange). Metaphase cells are marked with an asterisk and ana‐/telophase cells with a green bar. Representative confocal images of a metaphase, anaphase, and telophase cell stained for DNA, F‐actin, and α‐tubulin are shown at the bottom. d) Mean percentages of mitotic cells in metaphase and ana‐/telophase for the indicated conditions. The mean of 3–7 independent experiments is shown and error bars represent standard deviations. For the different conditions a minimum of 110 and maximum of 476 cells were analyzed individually.