Phosphorylation-mediated unfolding of a KH domain regulates KSRP localization via 14-3-3 binding

Abstract

The AU-rich-element (ARE)-mediated mRNA degradation activity of the RNA-binding Khomology Splicing Regulator Protein (KSRP) is regulated by phosphorylation of a serine within its N-terminal KH domain (KH1). In the cell phosphorylation promotes the interaction between KSRP and 14-3-3ζ protein and impairs the ability of KSRP to promote the degradation of its RNA targets. Here we examine the molecular details of this mechanism. We report that phosphorylation leads to the unfolding of the structurally atypical and unstable KH1, creating a site for 14-3-3 binding. Using this site 14-3-3 discriminates between phosphorylated and non phosphorylated KH1, driving the nuclear localization of KSRP. 14-3-3-KH1 interaction regulates the mRNA decay activity of KSRP by sequestering the protein in a separate functional pool. This study demonstrates how an mRNA degradation pathway is connected to extra cellular signaling networks by the reversible unfolding of a protein domain.

PreImplantation factor promotes neuroprotection by targeting microRNA let-7

“…AKT-mediated KSRP phosphorylation at a unique serine residue (S193) through PI3K/AKT signaling induces KSRP association with protein 14-3-3 and impairs KSRP's ability to promote target mRNA degradation (50). S193 phosphorylation leads to the unfolding of KSRP, creating a binding site for 14-3-3, which drives the nuclear localization of KSRP and prevents it from destabilizing mRNA in the cytoplasm (51). sPIF-induced destabilization of the KSRP protein involves proteasomes (Fig.…”

The Intrinsically Disordered N-terminal Region of AtREM1.3 Remorin Protein Mediates Protein-Protein Interactions

“…For example, 14-3-3 proteins can discriminate between phosphorylated and non-phosphorylated partners (58). Interaction of a 14-3-3 protein with the RNA-binding K-homology splicing regulator protein (KSRP) is promoted by phosphorylation of the latter, which drives relocalization of KSRP into the nucleus, where it performs its mRNA degrading activity (59). In other cases, phosphorylation of residues within ID regions mediates stimulus-specific degradation, as in the case of plant GRAS transcription factors (60,61).…”

The role of the 3' untranslated region in post-transcriptional regulation of protein expression in mammalian cells.

“…The link between domains is created by long and flexible inter-domain linkers and the orientation of these domains is not fixed, therefore this flexibility may enable the recognition of different targets. 58 Second, interaction of the two central domains (KH2-KH3) is oriented by the inter-domain linker meaning that the orientation of KH2 and KH3 domains is well-defined and this forms the structural core of the KSRP protein. 59 KSRP localization is influenced by phosphorylation of the KH1 domain that binds the 14-3-3zeta transporting protein.…”