U3 SnoRNA-mediated Degradation of ZBTB7A Regulates Aerobic Glycolysis in Isocitrate Dehydrogenase 1 Wild-type Glioblastoma Cells

Aims: The isocitrate dehydrogenase (IDH) phenotype is associated with reprogrammed energy metabolism in glioblastoma (GBM) cells. Small nucleolar RNAs (snoRNAs) are known to exert an important regulatory role in the energy metabolism of tumor cells. The purpose of this study was to investigate the role of C/D box snoRNA U3 and transcription factor zinc finger and BTB domain-containing 7A (ZBTB7A) in the regulation of aerobic glycolysis and the proliferative capacity of IDH1 wild-type (IDH1 ) GBM cells.

Methods: Quantitative reverse transcription PCR and western blot assays were utilized to detect snoRNA U3 and ZBTB7A expression. U3 promoter methylation status was analyzed via bisulfite sequencing and methylation-specific PCR. Seahorse XF glycolysis stress assays, lactate production and glucose consumption measurement assays, and cell viability assays were utilized to detect glycolysis and proliferation of IDH1 GBM cells.

Results: We found that hypomethylation of the CpG island in the promoter region of U3 led to the upregulation of U3 expression in IDH1 GBM cells, and the knockdown of U3 suppressed aerobic glycolysis and the proliferation ability of IDH1 GBM cells. We found that small nucleolar-derived RNA (sdRNA) U3-miR, a small fragment produced by U3, was able to bind to the ZBTB4 3'UTR region and reduce ZBTB7A mRNA stability, thereby downregulating ZBTB7A protein expression. Furthermore, ZBTB7A transcriptionally inhibited the expression of hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA), which are key enzymes of aerobic glycolysis, by directly binding to the HK2 and LDHA promoter regions, thereby forming the U3/ZBTB7A/HK2 LDHA pathway that regulates aerobic glycolysis and proliferation of IDH1 GBM cells.

Conclusion: U3 enhances aerobic glycolysis and proliferation in IDH1 GBM cells via the U3/ZBTB7A/HK2 LDHA axis.