PLK1 (Polo-like kinase 1) is a serine/threonine protein kinase that serves as a master regulator of mitotic cell cycle progression and cell division. PLK1 performs multiple critical functions throughout M phase, including regulation of centrosome maturation, spindle assembly, chromosome 16, and cytokinesis 1. The protein operates through a unique mechanism involving its polo-box domains, which recognize and bind to pre-phosphorylated substrates, allowing PLK1 to phosphorylate numerous target proteins essential for proper mitosis 1. PLK1 activity is sustained during mitosis by Checkpoint kinase 2 (Chk2), which directly phosphorylates PLK1 at T210 to maintain full kinase activity and ensure accurate chromosome 16 2. The kinase also plays a crucial role in the mitotic surveillance pathway by controlling the cytosolic availability of 53BP1, which monitors mitotic duration and activates p53-dependent cell cycle arrest when division takes too long 3. Additionally, PLK1 contributes to epigenetic centromere maintenance by promoting CENP-A deposition in early G1 phase 4. PLK1 is frequently overexpressed in various human cancers and correlates with poor prognosis, making it an attractive therapeutic target 15. The protein also regulates apoptosis by phosphorylating caspase-9, thereby inhibiting programmed cell death in airway smooth muscle cells 6.