SCFβTrCP mediates stress-activated MAPK-induced Cdc25B degradation

Abstract

Cdc25A, which is one of the three mammalian CDK-activating Cdc25 protein phosphatases (Cdc25A, B and C), is degraded through SCFβTrCP-mediated ubiquitylation following genomic insult; however, the regulation of the stability of the other two Cdc25 proteins is not well understood. Previously, we showed that Cdc25B is primarily degraded by cellular stresses that activate stress-activated MAPKs, such as Jun NH2-terminal kinase (JNK) and p38. Here, we report that Cdc25B was ubiquitylated by SCFβTrCP E3 ligase upon phosphorylation at two Ser residues in the βTrCP-binding-motif-like sequence D94AGLCMDSPSP104. Point mutation of these Ser residues to alanine (Ala) abolished the JNK-induced ubiquitylation by SCFβTrCP, and point mutation of DAG to AAG or DAA eradicated both βTrCP binding and ubiquitylation. Further analysis of the mode of βTrCP binding to this region revealed that the PEST-like sequence from E82SS to D94AG is crucially involved in both the βTrCP binding and ubiquitylation of Cdc25B. Furthermore, the phospho-mimetic replacement of all 10 Ser residues in the E82SS to SPSP104 region with Asp resulted in βTrCP binding. Collectively, these results indicate that stress-induced Cdc25B ubiquitylation by SCFβTrCP requires the phosphorylation of S101PS103P in the βTrCP-binding-motif-like and adjacent PEST-like sequences.