Rabbit Anti-Human EIF3L Polyclonal antibody

Oncogene-induced senescence (OIS) is an important tumor suppression mechanism preventing uncontrolled proliferation in response to aberrant oncogenic signaling. The profound functional and morphological remodelling of the senescent cell involves extensive changes. In particular, alterations in protein ubiquitination during senescence have not been systematically analyzed previously. Here, we report the first global ubiquitination profile of primary human cells undergoing senescence. We employed a well-characterized in vitro model of OIS, primary human fibroblasts expressing oncogenic RAS. To compare the ubiquitinome of RAS-induced OIS and controls, ubiquitinated peptides were enriched by immune affinity purification and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS). We identified 4,472 ubiquitination sites, with 397 sites significantly changed (>3 standard deviations) in senescent cells. In addition, we performed mass spectrometry analysis of total proteins in OIS and control cells to account for parallel changes in both protein abundance and ubiquitin levels that did not affect the percentage of ubiquitination of a given protein. Pathway analysis revealed that the OIS-induced ubiquitinome alterations mainly affected 3 signaling networks: eIF2 signaling, eIF4/p70S6K signaling, and mTOR signaling. Interestingly, the majority of the changed ubiquitinated proteins in these pathways belong to the translation machinery. This includes several translation initiation factors (eIF2C2, eIF2B4, eIF3I, eIF3L, eIF4A1) and elongation factors (eEF1G, eEF1A) as well as 40S (RPS4X, RPS7, RPS11 and RPS20) and 60S ribosomal subunits (RPL10, RPL11, RPL18 and RPL35a). In addition, we observed enriched ubiquitination of aminoacyl-tRNA ligases (isoleucyl-, glutamine-, and tyrosine-tRNA ligase), which provide the amino acid-loaded tRNAs for protein synthesis. These results suggest that ubiquitination affects key components of the translation machinery to regulate protein synthesis during OIS. Our results thus point toward ubiquitination as a hitherto unappreciated regulatory mechanism during OIS.

BackgroundAbnormal expression of the eukaryotic initiation factor 3 (eIF3) subunits plays critical roles in tumorigenesis and progression, and also has potential prognostic value in cancers. However, the expression and clinical implications of eIF3 subunits in glioma remain unknown.MethodsExpression data of eIF3 for patients with gliomas were obtained from the Chinese Glioma Genome Atlas (CGGA) (n=272) and The Cancer Genome Atlas (TCGA) (n=595). Cox regression, the receiver operating characteristic (ROC) curves and Kaplan-Meier analysis were used to study the prognostic value. Gene oncology (GO) and gene set enrichment analysis (GSEA) were utilized for functional prediction.ResultsIn both the CGGA and TCGA datasets, the expression levels of eIF3d, eIF3e, eIF3f, eIF3h and eIF3l highly were associated with the IDH mutant status of gliomas. The expression of eIF3b, eIF3i, eIF3k and eIF3m was increased with the tumor grade, and was associated with poorer overall survival [All Hazard ratio (HR)>1 and P<0.05]. By contrast, the expression of eIF3a and eIF3l was decreased in higher grade gliomas and was associated with better overall survival (Both HR<1 and P<0.05). Importantly, the expression of eIF3i (located on chromosome 1p) and eIF3k (Located on chromosome 19q) were the two highest risk factors in both the CGGA [eIF3i HR=2.068 (1.425-3.000); eIF3k HR=1.737 (1.166-2.588)] and TCGA [eIF3i HR=1.841 (1.642-2.064); eIF3k HR=1.521 (1.340-1.726)] databases. Among eIF3i, eIF3k alone or in combination, the expression of eIF3i was the more robust in stratifying the survival of glioma in various pathological subgroups. The expression of eIF3i was an independent prognostic factor in IDH-mutant lower grade glioma (LGG) and could also predict the 1p/19q codeletion status of IDH-mutant LGG. Finally, GO and GSEA analysis showed that the elevated expression of eIF3i was significantly correlated with the biological processes of cell proliferation, mRNA processing, translation, T cell receptor signaling, NF-B signaling and others.ConclusionsOur study reveals the expression alterations during glioma progression, and highlights the prognostic value of eIF3i in IDH-mutant LGG.