eIF3 Interacts with Selenoprotein mRNAs

Abstract

The synthesis of selenoproteins requires the co-translational recoding of an in-frame UGASec codon. Interactions between the Selenocysteine Insertion Sequence (SECIS) and the SECIS binding protein 2 (SBP2) in the 3′untranslated region (3′UTR) of selenoprotein mRNAs enable the recruitment of the selenocysteine insertion machinery. Several selenoprotein mRNAs undergo unusual cap hypermethylation and are not recognized by the translation initiation factor 4E (eIF4E) but nevertheless translated. The human eukaryotic translation initiation factor 3 (eIF3), composed of 13 subunits (a-m), can selectively recruit several cellular mRNAs and plays roles in specialized translation initiation. Here, we analyzed the ability of eIF3 to interact with selenoprotein mRNAs. By combining ribonucleoprotein immunoprecipitation (RNP IP) in vivo and in vitro with cross-linking experiments, we found interactions between eIF3 and a subgroup of selenoprotein mRNAs. We showed that eIF3 preferentially interacts with hypermethylated capped selenoprotein mRNAs rather than m7G-capped mRNAs. We identified direct contacts between GPx1 mRNA and eIF3 c, d, and e subunits and showed the existence of common interaction patterns for all hypermethylated capped selenoprotein mRNAs. Differential interactions of eIF3 with selenoprotein mRNAs may trigger specific translation pathways independent of eIF4E. eIF3 could represent a new player in the translation regulation and hierarchy of selenoprotein expression.

Comparative Proteomic Analysis Provides New Insights into the Molecular Basis of Thermal-Induced Parthenogenesis in Silkworm (Bombyx mori)

“…Comparative transcriptomic analysis between obligately asexual and cyclically asexual rotifers also revealed that the expression of genes encoding ribosomal proteins is higher in OP lines than in CP lines [ 26 ]. Furthermore, five gene expression-related proteins, including small nuclear ribonucleoprotein G [ 42 ], U6 snRNA-associated Sm-like protein isoform X1 [ 43 ], small nuclear ribonucleoprotein Sm S2 [ 44 ], eukaryotic translation initiation factor 3 subunit G [ 45 ], and deoxyhypusine hydroxylase/monooxygenase [ 46 ], were increased in abundance in PL. We suggested that the increase in translation process might facilitate parthenogenetic development when subjected to thermal stimuli.…”

A dynamic compositional equilibrium governs mRNA recognition by eIF3

“…mRNAs [13][14][15][16][17][18]25,36,[57][58][59][60][61] . These latter results motivated us to use our eIF3R system to ask whether individual eIF3R subcomplexes and/or subunits exhibit high-affinity mRNA binding and, if so, whether the dynamic eIF3 compositional equilibrium might regulate the ability of eIF3 to bind mRNA.…”

“…Several prior studies have suggested that eIF3 interacts with specific mRNAs dependent on sequence [12][13][14][15][16][17][18] . Seemingly in contrast, our anisotropy experiments testing the ability of eIF3 to bind a limited set of three mRNAs with distinct sequence content did not show a substantial difference in Kd app .…”

“…Eukaryotic translation initiation factor (eIF) 3 is a multi-subunit protein complex that is required for mRNA recruitment to the 43S PIC during initiation [6][7][8][9] . eIF3 has more recently been implicated in mediating events during translation elongation 10 and termination 11 , and has also emerged as a player in translational regulation at multiple stages and by various proposed mechanisms [12][13][14][15][16][17][18] . And yet, how the role of eIF3 in mRNA recruitment is related to these emerging regulatory roles and their underlying mechanism remains a mystery.…”