Abstract

Protein synthesis is mainly regulated at the initiation step, allowing the fast, reversible and spatial control of gene expression. Initiation of protein synthesis requires at least 13 translation initiation factors to assemble the 80S ribosomal initiation complex. Loss of translation control may result in cell malignant transformation. Here, we asked whether translational initiation factors could be regulated by NF-κB transcription factor, a major regulator of genes involved in cell proliferation, survival, and inflammatory response. We show that the p65 subunit of NF-κB activates the transcription of eIF4H gene, which is the regulatory subunit of eIF4A, the most relevant RNA helicase in translation initiation. The p65-dependent transcriptional activation of eIF4H increased the eIF4H protein content augmenting the rate of global protein synthesis. In this context, our results provide novel insights into protein synthesis regulation in response to NF-κB activation signalling, suggesting a transcription-translation coupled mechanism of control.

Highlights

  • IntroductionInitiation of protein synthesis of most eukaryotic mRNAs is m7G-cap-dependent and requires at least 13 eukaryotic initiation factors (eIFs) [1,2]

  • Protein synthesis is timely regulated at the step of translation initiation

  • Interaction of eIF4G with eIF3 recruits the 43S ribosomal complex to mRNA in order to generate the pre-initiation complex (PIC) that scans the mRNA in 59-39 direction towards the initiation codon, where PIC associates with the 60S ribosomal subunit to constitute the 80S initiation complex

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Summary

Introduction

Initiation of protein synthesis of most eukaryotic mRNAs is m7G-cap-dependent and requires at least 13 eukaryotic initiation factors (eIFs) [1,2]. The multiprotein complex, including eIF3, eIF1, eIF1A, eIF5 and eIF2–GTP–Met-tRNAMet, binds to the 40S ribosomal subunit to generate the 43S pre-initiation complex. Interaction of eIF4G with eIF3 recruits the 43S ribosomal complex to mRNA in order to generate the pre-initiation complex (PIC) that scans the mRNA in 59-39 direction towards the initiation codon, where PIC associates with the 60S ribosomal subunit to constitute the 80S initiation complex. Sliding of PIC along the mRNA requires the ATP-dependent RNA helicase eIF4A, which unwinds secondary structures that occur at the 59untranslated region of more than half of human mRNAs, and is required for scanning processivity of the 40S ribosomal subunit toward the initiation codon [2]. The homologous RNA binding proteins eIF4B and eIF4H associate with eIF4A in a mutually exclusive manner, and stimulate the eIF4A helicase activity [3,4]

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