Abstract 1289: CSDE1 mediated translation reprogramming under stress
Authors: Cui Jiajia , Guo Ao-Xiang , Wang Lei-Yun , Yin Ji-Ye 
Published: September 2020

Abstract
OBJECTIVE
To explore the role and underlying mechanisms of CSDE1 (cold shock domain containing E1) in translation reprogramming under stress on genome-wide level.
METHODS
Cell 2D culture, clone formation and 3D culture were used to detect cell growth viability. Would healing assay was used to detect cell migrating ability. Flow cytometer was used to detected cell apoptosis, ROS (reactive oxygen species) and lipid-ROS. Immunofluorescence assay was taken to investigate the intracellular localization of proteins. CO-IP assay and protein spectrum were conducted to study interactive proteins. GST pull down assay was carried out to further identify the interaction between proteins. EMSA was carried out to explore the interaction between proteins and RNAs. Polysome profiling was used to isolating the actively translating mRNA. Isolated RNA was sequenced by RNA-seq to identify the mRNA regulated by CSDE1 on translational level.
RESULTS
Changing CSDE1 expression had little effect on cell growth, migrating, invasion in normal conditions. Then the role of CSDE1 in stress conditions was explored. For starvation stress, cells were cultured with RPMI 1640 or PBS, CSDE1 had no effect on cell vitality compared with control group. For ROS stress induced by H2O2, CSDE1 has no effect on cell grow rate and intracellular ROS level as well. For anoxic stress, the expression of CSDE1 influenced the expression of Hif-1α and cell apoptosis. For ferroptosis stress, knocking down CSDE1 increased the lipid-ROS and cell death. For DNA damage stress, cisplatin was used to construct cellular DNA damage model. CSDE1 could protect cell from DNA damage in NER (nucleotide excision repair) and DSB (double strand break) pathway and then promote cell growth. For ER (endoplasmic reticulum) stress, cells were treated with thapsigargin, and CSDE1 expression was changed over time during ER. CSDE1 can regulate the expression of CHOP, PERK and GRP78 which acted as the key proteins of unfolded protein reaction whether knocking down or overexpressing CSDE1. Besides, CSDE1 can inhibit cell autophagy and apoptosis during ER stress. Then the mechanism of CSDE1 in stress conditions was further explored. Under DNA damage stress, both CSDE1 and eIF3a regulated the translation of RPA2. CSDE1 colocalized with eIF3a and they bound with each other by CSD1 domain of CSDE1 and PCI domain of eIF3a. Besides, it is CSDE1 domain, but not eIF3a domain that can bind to RPA2 IRES. Therefore, CSDE1 acted as a bridge to connect eIF3a and RPA2 IRES and reprogram RPA2 translation. Under ER stress, knocking down CSDE1 significantly increased translation activity according to polysome profiling assay. Similarly, CSDE1 acted as a bridge to connect some proteins and RNAs to reprogram the translation.
CONCLUSION
CSDE1 works as a bridge to connect different protein regulators and RNAs under different stress. In this way, it can play a key role in translation reprogramming and thus reprogram the cell fate.
Citation Format: Jiajia Cui, Ao-Xiang Guo, Lei-Yun Wang, Ji-Ye Yin. CSDE1 mediated translation reprogramming under stress [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1289.