Abstract A28: Oxygen-dependent translatome remodeling is controlled by eIF2α dephosphorylation

Abstract

Abstract Introduction: Eukaryotic translation initiation factor 2α (eIF2α) is a core component of the cellular translation machinery. Alterations in eIF2α phosphorylation constitute a key adaptation during a variety of physiological stresses, including oxygen deprivation (hypoxia). We recently found that cancer cells respond to hypoxia through the systemic reprogramming of cap-dependent mRNA translation efficiencies by switching to the hypoxic eIF4F, eIF4FH. In the present study, we sought to elucidate the role(s) of eIF2α phosphorylation and dephosphorylation in this translatome remodeling process. In particular, the growth arrest and DNA damage-inducible protein GADD34 has been reported as an adaptive, stress-activated mediator of eIF2α dephosphorylation. We aimed to determine the role of GADD34 in the cellular hypoxic response. Findings: Our results indicate that hypoxia-induced eIF2α phosphorylation is a transient response with corresponding effects on translation efficiencies. Using next-generation mRNA sequencing (mRNA-seq), we reveal the dynamic profile of the translatome remodeling process during acute and chronic hypoxia. Our findings demonstrate that GADD34-mediated eIF2α dephosphorylation is required for hypoxic protein synthesis. GADD34 silencing results in high levels of eIF2α phosphorylation and severe global translational inhibition. Notably, GADD34 regulates the translation of hypoxia-inducible proteins in a hypoxia-inducible factor 2α (HIF-2α)-dependent manner. Finally, high throughput mass spectrometry (MS) analysis reveals several potential hypoxia-regulated GADD34 post-translational modifications (PTMs). Efforts are underway to validate and determine the effect(s) of these PTMs on GADD34 protein stability and/or activity. Conclusion: We demonstrate that GADD34-mediated eIF2α dephosphorylation regulates oxygen-dependent translatome reprogramming in cancer cells. This pathway represents an exciting potential target for cancer therapeutics. Citation Format: J.J. David Ho, Nathan C. Balukoff, Grissel Cervantes, Ayalivis De La Rosa, Stephen Lee. Oxygen-dependent translatome remodeling is controlled by eIF2α dephosphorylation. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr A28.