Structure and function of phosphorylation-dependent interactions between PLK1 and the MRN complex

Polo-like kinase 1 (PLK1) is a serine/threonine kinase involved in the regulation of key cell cycle events involved in genome integrity maintenance, including centrosome maturation; G2-DNA damage recovery; mitotic entry; bipolar spindle assembly and cytokinesis. PLK1 is characterised by an amino-terminal Ser/Thr kinase domain and a carboxy-terminal catalytically inactive region, containing two adjoined structures, or so-called polo-box motifs, which form a 12-standed sandwich or polo-box domain (PBD). The PBD functions as a phospho-interaction module to facilitate recognition of and interaction with phosphoserine/threonine peptides generated via PLK1-induced (self-primed) or other Ser/Thr kinase-induced phosphorylation (non-self-primed). Through interaction with its cognate receptors, the PBD spatiotemporally regulates the subcellular localisation of PLK1, and thus the activity of the catalytic domain.