Regulatory subunit of serine/threonine-protein phosphatase 4. May play a role in regulation of cell division in renal glomeruli. The PPP4C-PPP4R1 PP4 complex may play a role in dephosphorylation and regulation of HDAC3. Plays a role in the inhibition of TNF-induced NF- kappa-B activation by regulating the dephosphorylation of TRAF2. . (Microbial infection) Participates in merkel polyomavirus- mediated inhibition of NF-kappa-B by bridging viral small tumor antigen with NEMO. . This is the function of PPP4R1 (protein phosphatase 4 regulatory subunit 1, ENSG00000154845).