Translational induction of ATF4 during integrated stress response requires noncanonical initiation factors eIF2D and DENR

Deepika Vasudevan,Sarah D Neuman,Arash Bashirullah,Brian Brown,Lea Lough,Amy Yang,Timothy Cardozo,Hyung Don Ryoo

doi:10.1038/s41467-020-18453-1

Deepika Vasudevan, Sarah D Neuman + Show 6 more

Open Access

https://doi.org/10.1038/s41467-020-18453-1

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Abstract

The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation. Such limiting conditions paradoxically stimulate the translation of ATF4 mRNA through a regulatory 5′ leader sequence with multiple upstream Open Reading Frames (uORFs), thereby activating stress-responsive gene expression. Here, we report the identification of two critical regulators of such ATF4 induction, the noncanonical initiation factors eIF2D and DENR. Loss of eIF2D and DENR in Drosophila results in increased vulnerability to amino acid deprivation, susceptibility to retinal degeneration caused by endoplasmic reticulum (ER) stress, and developmental defects similar to ATF4 mutants. eIF2D requires its RNA-binding motif for regulation of 5′ leader-mediated ATF4 translation. Consistently, eIF2D and DENR deficient human cells show impaired ATF4 protein induction in response to ER stress. Altogether, our findings indicate that eIF2D and DENR are critical mediators of ATF4 translational induction and stress responses in vivo.

Highlights

The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation
We demonstrate that the loss of eIF2D and Density-regulated reinitiation and release factor (DENR) disrupts a number of pathophysiological processes in Drosophila that require ATF4 signaling
During translation of mRNAs with multiple upstream Open Reading Frames (uORFs), such as those seen in the ATF4 5′ leader, the scanning ribosome consumes the Met-tRNAiMet upon encountering the uORFs

Summary

Introduction

The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation. The results from the screen were confirmed in dissected fat body tissues, which had decreased 4E-BPintron-dsRed signal upon knockdown of eIF2D without affecting control GFP expression (Fig. 1h, i). Fat body-specific expression of crcleaderless, but not a control transgene (lacZ), in eIF2D mutants restored the expression of 4E-BPintron-dsRed (Supplementary Fig. 2).

Results

Conclusion