MASTL (Microtubule Associated Serine/Threonine Kinase-Like), also known as Greatwall kinase, is a key enzyme in cell cycle regulation, primarily localized in the cell nucleus. It maintains the activity of serine/threonine kinases by phosphorylating and inhibiting PP2A-B55, thereby facilitating the normal progression of the M phase of the cell cycle. MASTL is expressed in a variety of cell types and tissues, playing a crucial role in ensuring accurate chromosome segregation and cell division. Specific expression and mutations in the gene can disrupt the normal cell cycle process and are potentially linked to the development of cancer and other diseases. Research into the regulatory mechanisms of MASTL offers possibilities for developing new cancer treatment strategies.