PLK

PLK inhibitors act on polo-like kinases (PLKs), serine/threonine kinases that coordinate mitosis and cytokinesis. The founding gene, polo, was described in Drosophila in 1991 as a protein kinase homolog required for mitosis. In PLK1, the most widely studied human member, a C-terminal polo-box domain (PBD) binds phosphorylated partner proteins and directs the kinase to its sites of action. BI 2536, reported in 2007, competes with adenosine triphosphate (ATP) and arrests cells in prometaphase. Volasertib, GSK461364 and TAK-960 are further ATP-competitive inhibitors used to study PLK1 in mitosis. Poloxin, described in 2008, works differently by blocking protein interactions that depend on the PBD.