61 Functional characterization of ribosomal RNA methyltransferase NSUN5 in glioblastoma

Abstract

Glioblastoma is the most common and malignant brain tumor with a median overall survival of 20.5 months. There is an urgent need to develop novel therapeutic strategies. Using a glioblastoma TCGA dataset, we have determined that high NSUN5 mRNA expression is strongly associated with poor survival in glioblastoma patients. NSUN5 is a ribosomal RNA (rRNA) cytosine methyltransferase. Human NSUN5 is located in chromosome 7 and is completely deleted in the Williams-Beurren syndrome, a complex neurodevelopmental disorder. However, RNA targets of NSUN5 in mammals and its role in cancer are unknown. The objective of this project is to determine whether elevated NSUN5 changes rRNA methylation pattern and thereby leads to pro-tumorigenic translational reprogramming and pro-tumorigenic phenotypes in glioblastoma. Western blotting showed that NSUN5 is expressed in 7 out of 9 established glioblastoma cell lines and in 8 out of 12 primary patient-derived glioblastoma cell lines. Bisulfite sequencing confirmed that NSUN5 methylates C3782 of human 28S rRNA in glioblastoma cells. Functionally, overexpression of NSUN5 increases, whereas NSUN5 knockout decreases global protein synthesis and sphere formation in glioblastoma cells. More importantly, mice bearing intracranial NSUN5-expressing U87 tumors survived for a shorter time than mice bearing tumors derived from U87 control cells. Our results suggest that NSUN5 methylates 28S rRNA and may enhance cancer stem cell phenotypes and tumor formation and/or progression in glioblastoma. Experiments are ongoing to determine whether NSUN5 promotes tumor formation and/or progression through translational reprogramming in glioblastoma. This study may help identify novel therapeutic targets for glioblastoma.

The Emerging Roles of RNA Modifications in Glioblastoma

“…However, "zipcode"-like sorting signals in RNA that mediate the enrichment of mRNAs in exosomes of GBM cells [126] may probably be recognized by cytosolic Y-box binding protein 1 (YB-1) and NSUN2 [127]. NSUN5, another RNA methyltransferase that is responsible for m 5 C in the C3782 position of human 28S rRNA, undergoes epigenetic loss in gliomas, which drives an overall depletion of protein synthesis, resulting in an adaptive translational program for survival under cellular stress and renders gliomas sensitive to bio-activatable substrates of the stress-related enzyme NAD(P)H quinone dehydrogenase 1 (NQO1) [81,82]. The m 5 C reader, ALYREF, may be an overexpressed antigen in GBM, according to a study with a nanobody-based anti-proteome approach [83] and is upregulated in recurrent GBM, according to a transcriptome analysis [84], implying it may be a promising drug target for GBM.…”

A novel prognostic risk-scoring system based on m5C methylation regulator-mediated patterns for glioma patients

“…A total of 14 m 5 C regulators or related genes were systematically searched from various reports and the literature: 11 writers, 1 eraser, and 2 readers ( NSUN1 , NSUN2 , NSUN3 , NSUN4 , NSUN5 , NSUN6 , NSUN7 , DNMT1 , DNMT2 , DNMT3A , DNMT3B , TET2 , ALYREF , and YBX1 ). 7 , 9 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 Ten of them were detected from the test dataset (TCGA-GBM) and finally utilized to construct the m 5 C modification patterns. Unsupervised clustering analysis was employed to identify distinct patterns (m 5 C cluster) based on the gene expression of the 10 regulators and to classify glioma patients into different distinct patterns.…”