Abstract A63: YB-1 is critical for stress granule assembly and protects cells from oxidative stress

Stress granules (SGs) are highly conserved cytoplasmic ribonucleoprotein complexes that modulate gene expression and cellular homeostasis under prototypical stress forms. SG formation protects cells under stress conditions by protecting untranslated mRNAs until stress relief, and cells that are incapable of forming SGs are more vulnerable to diverse stressors compared to cells that are proficient at SG formation. The transcription and translation regulation factor Y-box binding protein 1 (YB-1) is recruited to SG, but its exact contribution to formation of these structures is not clear. Using several stress inducing agents, arsenite, H 2 O 2 , piperlongumine, thapsigargin, heat shock, curcumin and hypoxia we demonstrate that YB-1 co-localizes to SG along with G3BP, TIA-1 and poly(A) + mRNA in various human cancer cell lines. YB-1 inactivation by siRNA knockdown dramatically reduces the efficiency of SG assembly in two sarcoma cell lines, U2OS and Rh-30 and a prostate cancer cell line DU-145, with high YB-1 expression. We also found that si-YB-1 cells with an inefficient stress granule formation were more sensitive to stress induced by arsenite, H 2 O 2 , or piperlongumine compared to control cells. YB-1 influences SG assembly via two distinct mechanisms. First, it acts as a scaffold protein to recruit mRNA and SG associated RNA-binding proteins into SGs. Second, YB-1 regulates the mRNA translation of the essential nucleator SG proteins, G3BP and TIA-1, thus controlling their availability during SG assembly under oxidative stress. Finally, in vivo , downregulation of YB-1 significantly affected the formation of stress granules in primary tumors generated in mice. Taken together, YB-1 is critical in SG formation and cell survival. Citation Format: Syam Prakash Somasekharan, Gabriel Leprivier, Valentina Evdokimova, Amal EI-Naggar, Shamil Hajee, Martin Gleave, Poul HB Sorensen. YB-1 is critical for stress granule assembly and protects cells from oxidative stress. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A63.