Illumination of mitotic orchestra during cell division: a Polo view.

Protein kinase and phosphatase signaling cascade, coupled with other post-translational modifications, orchestrates temporal order of various events during cell division. Among the many mitotic kinases, Polo-like kinase 1 (PLK1) as a key regulator, participates in regulating mitosis from mitotic entry to cytokinesis. The advancement in optical reporter engineering and the recent development of specific chemical probes enable us to visualize spatiotemporal gradient of kinase activity at nano-scale. One of such tools is FRET-based optic sensor that allows us to delineate the PLK1 activity in space and time. In this review, we address the inter-relationships between PLK1 and other protein kinases/phosphatases, as well as the crosstalk between PLK1 phosphorylation and ubiquitination during cell division. In particular, we discuss the molecular mechanisms and steps underlying PLK1 kinase priming, activation and turn-off during cell division.