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Cancer associated mRNAs regulated by the Helix Loop Helix motif of human EIF3A

ABSTRACT: Improper regulation of translation initiation, a vital check-point of protein synthesis in the cell, has been linked to a number of cancers. Overexpression of protein subunits of eukaryotic translation initiation factor 3 (eIF3) has been associated with increased translation of mRNAs involved in cell proliferation. In addition to playing a major role in general translation initiation by serving as a scaffold for the assembly of translation initiation complexes, eIF3 regulates translation of specific cellular mRNAs and viral RNAs. Mutations in the N-terminal Helix-Loop-Helix (HLH) RNA-binding motif of the EIF3A subunit in eIF3 interfere with Hepatitis C Virus Internal Ribosome Entry Site (IRES) mediated translation initiation in vitro. Here we use RNA-seq and ribosome profiling of engineered lentiviral HEK293T cells to show that the EIF3A HLH motif controls translation of a small set of cellular transcripts enriched in oncogenic mRNAs, including MYC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE118239 | GEO | 2018/08/08

REPOSITORIES: GEO

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Project description:The eukaryotic translation initiation factor (eIF) 3a is described in various tumor entities as potential tumor marker involved in development and progression of cancer. eIF3a is the largest subunit of the eIF3 complex, a key functional entity in 80S establishment and translation initiation. We hypothesize that eIF3a is more a specific than global translation initiator and involved in signalling pathways that are frequently targeted in UBC therapy. Methods: In FFPE samples of UBC patients eIF3a expression was analysed together with overall survival. In cell culture we investigated proliferation, migration, clonogenicity and tumorgenicity of UBC cell lines with and without knockdown of eIF3a and compared the cytotoxicity of eIF3a knockdown with other translational inhibitors, including the chemotherapeutic Rapamycine. Detailed information on changed gene expression and global translation initiation were gathered by mRNA expresssion and polysomal profiling. Results: and Conclusion eIF3a is upregulated in UBC and high expression of eIF3a corresponds with longer overall survival in low grade tumors. Knockdown of eIF3a in UBC cell lines reduces their malignant phenotype, including reduced tumor growth in xenotransplanted mice. eIF3a regulates DNA damage response (ATM, ATR, CDC25A) on a translational level and we show that reduction in eIF3a expression does not hamper global translation initiation. The knockdown of eIF3a strongly influences proliferation of UBC cell lines without dramatically disturbing general translation as depicted in polysomal profiles. We therefore analysed potential changes on the mRNA level in eIF3a knockdown compared to control HT1197 cells. Differential expression of genes between eIF3a knock-down and control samples was assessed with the moderated t-test (Bioconductor's limma package). Raw p-values were adjusted for multiple hypothesis testing using the method from Benjamini and Hochberg for a strong control of the false discovery rate.

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Cancer associated mRNAs regulated by the Helix Loop Helix motif of human EIF3A

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