Translation termination efficiency modulates ATF4 response by regulating ATF4 mRNA translation at 5' short ORFs

Area of Science:

• Molecular Biology
• Cellular Biology
• Genetics

Background:

• Activating transcription factor 4 (ATF4) is a key regulator of cellular stress responses.
• ATF4 expression is primarily controlled at the translational level via upstream open reading frames (uORFs) in its 5'-untranslated region (5'-UTR).
• Eukaryotic release factor 3a (eRF3a) plays a crucial role in translation termination.

Purpose of the Study:

• To investigate the mechanism regulating ATF4 expression in human cells with impaired translation termination.
• To elucidate the role of eRF3a in ATF4 translational control and its downstream effects.
• To understand how eRF3a depletion impacts the mTOR signaling pathway.

Main Methods:

• Microarray analysis of total RNA and polysome-associated mRNAs.
• Depletion of eukaryotic release factor 3a (eRF3a) in human cells.
• Analysis of ATF4 and ATF4 target gene expression.
• Investigation of REDD1 expression and mTOR pathway activity.

Main Results:

• Depletion of eRF3a leads to the upregulation of ATF4 and its target genes.
• eRF3a depletion alters translational control at ATF4 uORFs, enhancing ATF4 open reading frame (ORF) translation.
• Increased REDD1 expression in eRF3a-depleted cells mediates mTOR pathway inhibition.
• ATF4 activation occurs independently of the canonical eIF2α phosphorylation pathway.

Conclusions:

• eRF3a plays a critical role in modulating ATF4 translation, particularly in cells with compromised termination.
• Variations in translation termination efficiency can regulate ATF4-mediated responses in mammals.
• This study reveals a novel mechanism linking translation termination to the mTOR pathway via ATF4 regulation.