Hsp27 and F-Box Protein beta-TrCP Promote Degradation of mRNA Decay Factor AUF1

作者：Li Mei Ling; Defren Jennifer; Brewer Gary^*

来源：Molecular and Cellular Biology, 2013, 33(11): 2315-2326.

DOI：10.1128/MCB.00931-12

Activation of the mitogen-activated protein (MAP) pathway kinases p38 and MK2 induces phosphorylation of the chaperone Hsp27 and stabilization of mRNAs containing AU-rich elements (AREs) (ARE-mRNAs). Likewise, expression of phosphomimetic mutant forms of Hsp27 also stabilizes ARE-mRNAs. It appears to perform this function by promoting degradation of the ARE-mRNA decay factor AUF1 by proteasomes. In this study, we examined the molecular mechanism linking Hsp27 phosphorylation to AUF1 degradation by proteasomes. AUF1 is a target of beta-TrCP, the substrate recognition subunit of the E3 ubiquitin ligase Skp1-cullin-F-box protein complex, SCF beta-TrCP. Depletion of beta-TrCP stabilized AUF1. In contrast, overexpression of beta-TrCP enhanced ubiquitination and degradation of AUF1 and led to stabilization of reporter mRNAs containing cytokine AREs. Enhanced AUF1 degradation required expression of phosphomimetic mutant forms of both Hsp27 and AUF1. Our results suggest that a signaling axis composed of p38 MAP kinase-MK2-Hsp27-beta-TrCP may promote AUF1 degradation by proteasomes and stabilization of cytokine ARE-mRNAs.

• 出版日期2013-6