Distinct recruitment of human eIF4E isoforms to processing bodies and stress granules

Abstract

BackgroundEukaryotic translation initiation factor 4E (eIF4E) plays a pivotal role in the control of cap-dependent translation initiation, modulates the fate of specific mRNAs, occurs in processing bodies (PBs) and is required for formation of stress granules (SGs). In this study, we focused on the subcellular localization of a representative compendium of eIF4E protein isoforms, particularly on the less studied members of the human eIF4E protein family, eIF4E2 and eIF4E3.ResultsWe showed that unlike eIF4E1, its less studied isoform eIF4E3_A, encoded by human chromosome 3, localized to stress granules but not PBs upon both heat shock and arsenite stress. Furthermore, we found that eIF4E3_A interacts with human translation initiation factors eIF4G1, eIF4G3 and PABP1 in vivo and sediments into the same fractions as canonical eIF4E1 during polysome analysis in sucrose gradients. Contrary to this finding, the truncated human eIF4E3 isoform, eIF4E3_B, showed no localization to SGs and no binding to eIF4G. We also highlighted that eIF4E2 may exhibit distinct functions under different stresses as it readily localizes to P-bodies during arsenite and heat stresses, whereas it is redirected to stress granules only upon heat shock. We extended our study to a number of protein variants, arising from alternative mRNA splicing, of each of the three eIF4E isoforms. Our results surprisingly uncovered differences in the ability of eIF4E1_1 and eIF4E1_3 to form stress granules in response to cellular stresses.ConclusionOur comparison of all three human eIF4E isoforms and their protein variants enriches the intriguing spectrum of roles attributed to the eukaryotic initiation translation factors of the 4E family, which exhibit a distinctive localization within different RNA granules under different stresses. The localization of eIF4E3_A to stress granules, but not to processing bodies, along with its binding to eIF4G and PABP1 suggests a role of human eIF4E3_A in translation initiation rather than its involvement in a translational repression and mRNA decay and turnover. The localization of eIF4E2 to stress granules under heat shock but not arsenite stress indicates its distinct function in cellular response to these stresses and points to the variable protein content of SGs as a consequence of different stress insults.Electronic supplementary materialThe online version of this article (doi:10.1186/s12867-016-0072-x) contains supplementary material, which is available to authorized users.

Identifying the Translatome of Mouse NEBD-Stage Oocytes via SSP-Profiling; A Novel Polysome Fractionation Method

“…Figure S7. Reduced-sized-, 5-mL-SW55Ti ultracentrifugation tubes can accommodate enough cell lysate to detect moderately abundant protein in polysome profile fractions (contains the following references: [76][77][78]; Table S1. List of expressed genes with mean FPKM higher than 0.1 in at least one dataset; Table S2.…”

Distinct role of 5’UTR sequences in dendritic trafficking of BDNF mRNA: additional mechanisms for the BDNF splice variants spatial code.

“…PABP3 is a less studied member of the poly(A)-binding protein family with a slightly lower affinity to poly(A) as compared to the best-characterized isoform PABP1 and belongs to the mRNA 3'End Processing Factors required for the process of polyadenylation involved in mRNA translation (16). As PABP1 was shown to regulate the nuclear export of mRNAs towards the cytoplasm (17), and formation of P-bodies (18) it is plausible that also PABP3 may play a role either in cytoplasmic mRNA trafficking or translational regulation, or both. SNRNP70 belongs to the family of small nuclear nucleoproteins that bind to the spliceosomal U1 RNA, forming the core of the spliceosome.…”

RNA regulatory processes in RNA virus biology

“…Rabies virus infections induce stress granule formation near viral factories in Negri bodies which appears to be have a weak antiviral effect as TIA‐1 can block viral translation (Blondel et al, ). Overall, G3BP1‐enriched stress granules are induced during some RNA viral infections with both positive and negative effects on viral replication (Albornoz et al, ; Amorim, Temzi, Griffin, & Mouland, ; Bhowmick et al, ; Chahar et al, ; Courtney, Scherbik, Stockman, & Brinton, ; Dougherty et al, ; Frydryskova et al, ; Hou et al, ; Hu et al, ; Kim et al, ; Lavut & Raveh, ; Mok et al, ; Nelson et al, ; Pager et al, ; Panas et al, ; Pérez‐Vilaró et al, ; Rabouw et al, ; Sage et al, ; Scholte et al, ; Xia, Chen, Xu, et al, ; Zhou et al, ). Taken together these data show the need to effectively address the knowledge gap of the impact of stress granules on RNA virus infections.…”