Recruitment of the 4EHP-GYF2 cap-binding complex to tetraproline motifs of tristetraprolin promotes repression and degradation of mRNAs with AU-rich elements

Abstract

The zinc finger protein tristetraprolin (TTP) promotes translation repression and degradation of mRNAs containing AU-rich elements (AREs). Although much attention has been directed toward understanding the decay process and machinery involved, the translation repression role of TTP has remained poorly understood. Here we identify the cap-binding translation repression 4EHP-GYF2 complex as a cofactor of TTP. Immunoprecipitation and in vitro pull-down assays demonstrate that TTP associates with the 4EHP-GYF2 complex via direct interaction with GYF2, and mutational analyses show that this interaction occurs via conserved tetraproline motifs of TTP. Mutant TTP with diminished 4EHP-GYF2 binding is impaired in its ability to repress a luciferase reporter ARE-mRNA. 4EHP knockout mouse embryonic fibroblasts (MEFs) display increased induction and slower turnover of TTP-target mRNAs as compared to wild-type MEFs. Our work highlights the function of the conserved tetraproline motifs of TTP and identifies 4EHP-GYF2 as a cofactor in translational repression and mRNA decay by TTP.

Cap-binding protein 4EHP effects translation silencing by microRNAs

“…A similar mechanism functions in the mouse, where 4EHP binds the Prep1 RNA-binding protein and inhibits Hoxb4 mRNA translation (25). Moreover, 4EHP forms a translational repressor complex with GIGYF2 (Grb10-interacting GYF protein 2), which acts as a cofactor in translational repression and mRNA decay of tristetraprolin-targeted mRNAs (26,27).In this work, we demonstrate that 4EHP interacts with the mRNA-silencing machinery and engenders miRNA-mediated translational repression. Our data support a model wherein 4EHP interactions with miRISC/CCR4-NOT lead to the translational repression of miRNA targets.…”

“…For instance, the GIGYF1/2 and 4E-T proteins bind to the same motif on the 4EHP protein and thus GIGYF1/2 must compete with 4E-T for this binding site. The GIGYF1/2-4EHP complex had been characterized as a translational repressor, notably as a cofactor of tristetraprolin (26,27). Interestingly, human GIGYF1/2 and the related yeast protein Smy2 also associate with CCR4-NOT (39,40).…”

“…A similar mechanism functions in the mouse, where 4EHP binds the Prep1 RNA-binding protein and inhibits Hoxb4 mRNA translation (25). Moreover, 4EHP forms a translational repressor complex with GIGYF2 (Grb10-interacting GYF protein 2), which acts as a cofactor in translational repression and mRNA decay of tristetraprolin-targeted mRNAs (26,27).…”

GIGYF1/2 proteins use auxiliary sequences to selectively bind to 4EHP and repress target mRNA expression

“…′ untranslated regions (UTRs) by tristetraprolin (TTP) (Tao and Gao 2015;Fu et al 2016). Thus, through its association with diverse binding partners, 4EHP regulates the translation of mRNAs involved in a broad range of biological process, and disruption of its expression results in perinatal lethality in mice (Morita et al 2012).…”

An Ancient Family of RNA-Binding Proteins: Still Important!

“…Other critical sequence regions that are present in the mammalian proteins, and that may need to be accounted for in proteins from other species, include a leucine-rich nuclear export sequence, involved in nuclear-cytoplasmic shuttling [36, 37], and specific phosphorylated serine and threonine residues that are critical for the interaction of the mammalian proteins with 14-3-3- proteins, important for the regulation of protein activity in the cell [29, 38]. In the case of TTP, a conserved domain specific to TTP, the tetraproline (PPPPG) motif, has been implicated in the regulation of translation through its interaction with the translation repression complex, 4EHP-GYF2 [39]. This tetraproline motif has been shown to bind to the GYF2 subunit of 4EHP-GYF2.…”