Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 108, Issue 22, Pages 9310-9315Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1101112108
Keywords
mitotic kinase; macromolecular assembly; reaction-diffusion mechanism
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Funding
- Wellcome Trust
- Medical Research Council
- MRC [MC_U105359877, G0700651, G0600332, G9900064] Funding Source: UKRI
- Medical Research Council [G9900064, G0600332, MC_U105359877, G0700651] Funding Source: researchfish
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Whether mitotic structures like the centrosome can self-organize from the regulated mobility of their dynamic protein components remains unclear. Here, we combine fluorescence spectroscopy and chemical genetics to study in living cells the diffusion of polo-like kinase 1 (PLK1), an enzyme critical for centrosome maturation at the onset of mitosis. The cytoplasmic diffusion of a functional EGFP-PLK1 fusion correlates inversely with known changes in its enzymatic activity during the cell cycle. Specific EGFP-PLK1 inhibition using chemical genetics enhances mobility, as do point mutations inactivating the polo-box or kinase domains responsible for substrate recognition and catalysis. Spatial mapping of EGFP-PLK1 diffusion across living cells, using raster image correlation spectroscopy and line scanning, detects regions of low mobility in centrosomes. These regions exhibit characteristics of increased transient recursive EGFP-PLK1 binding, distinct from the diffusion of stable EGFP-PLK1-containing complexes in the cytoplasm. Chemical genetic suppression of mitotic EGFP-PLK1 activity, even after centrosome maturation, causes defects in centrosome structure, which recover when activity is restored. Our findings imply that continuous PLK1 activity during mitosis maintains centrosome self-organization by a mechanism dependent on its reaction and diffusion, suggesting a model for the formation of stable mitotic structures using dynamic protein kinases.
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