INT6 interacts with MIF4GD/SLIP1 and is necessary for efficient histone mRNA translation

Abstract

The INT6/EIF3E protein has been implicated in mouse and human breast carcinogenesis. This subunit of the eIF3 translation initiation factor that includes a PCI domain exhibits specific features such as presence in the nucleus and ability to interact with other important cellular protein complexes like the 26S proteasome and the COP9 signalosome. It has been previously shown that INT6 was not essential for bulk translation, and this protein is considered to regulate expression of specific mRNAs. Based on the results of a two-hybrid screen performed with INT6 as bait, we characterize in this article the MIF4GD/SLIP1 protein as an interactor of this eIF3 subunit. MIF4GD was previously shown to associate with SLBP, which binds the stem-loop located at the 39 end of the histone mRNAs, and to be necessary for efficient translation of these cell cycle-regulated mRNAs that lack a poly(A) tail. In line with the interaction of both proteins, we show using the RNA interference approach that INT6 is also essential to S-phase histone mRNA translation. This was observed by analyzing expression of endogenous histones and by testing heterologous constructs placing the luciferase reporter gene under the control of the stem-loop element of various histone genes. With such a reporter plasmid, silencing and overexpression of INT6 exerted opposite effects. In agreement with these results, INT6 and MIF4GD were observed to colocalize in cytoplasmic foci. We conclude from these data that INT6, by establishing interactions with MIF4GD and SLBP, plays an important role in translation of poly(A) minus histone mRNAs.

The role of eIF3 and its individual subunits in cancer

“…eIF3e also has been shown to promote the binding of the kinase Mnk1 to eIF4G and its subsequent phosphorylation of eIF4E [107]. In addition to binding to eIF4G, 3e interacts with the stress-and interferon-inducible translation inhibitory protein P56 [108], with the MIF4GD/SLIP12 proteins involved in the translation of histone mRNAs that lack the poly(A) tail [109], with the Ca ++ voltage-gated channel protein CaV1.2 [110], with the DNA damage protein ATM [111] and with the cell growth proteins, TID1 and Patched [112]. eIF3e also is involved in nonsense mediated decay of mRNAs [113], and reduced levels appear to specifically down-regulate the synthesis of Hypoxia-inducible factors (HIFs) [104].…”

Coupling 40S ribosome recruitment to modification of a cap-binding initiation factor by eIF3 subunit e

“…GENES & DEVELOPMENT Cold Spring Harbor Laboratory Press on May 12, 2018 -Published by genesdev.cshlp.org Downloaded from and specific mRNA translation (Asano et al 1997;Rasmussen et al 2001;Mayeur and Hershey 2002;Udagawa et al 2008;Grzmil et al 2010;Chiluiza et al 2011;Suo et al 2011;Neusiedler et al 2012). Indeed, eIF4E phosphorylation exerts differential effects on mRNA translation and plays important roles in cell proliferation, transformation, immune responses, and viral infection Mohr 2004, 2011;Wendel et al 2007;Furic et al 2010;Ueda et al 2010;Herdy et al 2012).…”

Replication stress-induced alternative mRNA splicing alters properties of the histone RNA-binding protein HBP/SLBP: a key factor in the control of histone gene expression

“…The region Lys 65 –Gln 82 of Xenopus SLBP1 is important for translation and the interaction with SLIP1, a factor specifically involved in translation of histone mRNA [21,22,24]. The alignment of the N-terminal sequences of human, chicken and zebrafish HBP/SLBP and Xenopus SLBP1 indicates that this region encoded by exon 3 is conserved in chicken, zebrafish and human proteins (Figure 4).…”

“…HBP/SLBP is thought to interact with a histone mRNA specific translation factor called SLIP1 (SLBP-interacting protein 1, or MIF4GD (MIF4G domain)-containing protein) as well as with eIF3 (eukaryotic initiation factor 3) and PAIP1 (polyadenylate-binding protein-interacting protein 1) [21,22,24]. It has been proposed that HBP/SLBP binds SLIP1 that in turn binds the 5′ cap-binding protein, eIF4E and hence circularises the mRNA.…”