PME-1 (Protein Phosphatase Methylesterase-1) is an enzyme involved in the dephosphorylation process, part of the regulatory subunit of PP2A (Protein Phosphatase 2A). It is primarily located in the cell nucleus, where it regulates PP2A activity through demethylation, affecting processes such as cell growth, division, and death. The activity and expression levels of PME-1 vary among different cell types and tissues, with this specific expression being crucial for maintaining the balance of intracellular signaling. Genetic mutations or expression dysregulation can lead to cell cycle abnormalities, associated with the development of various diseases.