The protein serine/threonine phosphatase complex PP2A, recruited to MDM2 through interaction of the PP2A regulatory subunit PPP2R5C and cyclin G1 (CCNG1) dephosphorylates MDM2 on threonine residue T218 (T218 in human MDM2 corresponds to T216 in mouse Mdm2). Dephosphorylation of T218 increases the affinity of MDM2 for TP53 (p53), leading to p53 down-regulation (Okamoto et al. 2002).
CCNG1-recruited PP2A can also dephosphorylate serine residue S166 of human MDM2 (Okamoto et al. 2002).