Protein Phosphatase 1A (PPM1A) is a member of the PP2C family of Ser/Thr protein phosphatases which are known to be negative regulators of cell stress response pathways. PPM1A has a broad specificity. PPM1A negatively regulates the activities of MAP kinases and MAP kinase kinases. Also, it negatively regulates TGF-beta signaling through dephosphorylating SMAD2 and SMAD3, resulting in their dissociation from SMAD4, nuclear export of the SMADs and termination of the TGF-beta-mediated signaling. In addition, PPM1A can dephosphorylate cyclin-dependent kinases, and thus may be involved in cell cycle control.