Mitogen-activated protein kinase (MAPK) phosphatases [MKPs, also known as dual-specificity phosphatases (DUSPs)] regulate MAPKs -key mediators of cellular processes such as proliferation, differentiation, and survival- by dephosphorylating the threonine and tyrosine residues required for MAPK activation. MKP-3/DUSP6 is an ERK-selective phosphatase that has also been reported to regulate the transcription factor FOXO1. The full-length MKP-3 transcript has been shown to encode the MKP-3L protein, ...