Abstract 153: Epigenetic loss of NSUN5 in glioma drives a global protein synthesis depletion along with the emergence of a stress adaptive translational program

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Abstract One of the known hallmarks of cancer is an aberrant RNA transcriptome, and yet, it cannot always be fully due to genetic or epigenetic alterations at the transcriptional start sites of the genes. Indeed, recent evidences point out to new malignant alterations at the RNA level itself. RNA molecules have been found to show more than 100 differently chemically modified nucleotides, and such post-transcriptional modifications play a role in controlling RNA homeostasis, being all grouped under the term ‘epitranscriptome'. In our study, we reported that human glioma cells undergo DNA methylation-associated epigenetic silencing of NSUN5, a candidate 5-methylcytosine RNA methyltransferase. As NSUN5 activity has not been formally described in human cells yet, we studied its potential targets in the human transcriptome, demonstrating its role in the methylation of the cytosine 3782 in the 28S ribosomal RNA (rRNA). Logically, we found that NSUN5 loss generates an unmethylated status at the C3782 position of 28S rRNA, and this depletion drives an overall depletion of protein synthesis under stress conditions, analyzed by O-propargyl-puromycin (OP-Puro) and [3H] leucine incorporation into nascent proteins. However, together with the depletion of global protein synthesis, we observed the emergence of an adaptive translational program for survival under conditions of cellular stress, assessed by combining three NGS-experiments: RNA-seq, Ribo-seq and SILAC. Moreover, as one of the genes increasing its expression upon NSUN5 silencing is the stress-related enzyme NQO1, we found out that NSUN5-depleted gliomas are sensitive to bioactivatable substrates of the NQO1 enzyme. Most importantly, we observed that NSUN5 epigenetic inactivation is a hallmark of glioma patients with long-term survival, conferring it value as a predictor of better patient outcome for this otherwise devastating disease. Citation Format: Vanessa Ortiz Barahona, Maxime Janin, Manel Esteller. Epigenetic loss of NSUN5 in glioma drives a global protein synthesis depletion along with the emergence of a stress adaptive translational program [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 153.