Showcase of Undergraduate Research and Creative Endeavors (SOURCE)

Stabilizing G4 Structures Increases RYBP Transcription in Cancerous Glial Cells

Glioblastoma multiforme (GBM) is a malignant brain cancer of glial cells in the central nervous system, and it has a median survival of less than 15 months. When compared to healthy glial cells, GBM tumors significantly downregulate RING1 and YY1 binding protein (RYBP). However, the mechanism of RYBP transcriptional silencing in GBM remains unknown. G-quadruplexes (G4s) are guanine-rich sequences that fold in DNA and RNA to create stable secondary structures. When present in gene promoters, G4s can behave as switches that modulate transcription. Therefore, to determine whether G4s contribute to RYBP silencing, we analyzed the RYBP promoter sequence and found two putative G4-forming sequences. We treated U-87, U-118, and T98-G cell lines with the G4-stabilizing ligands PHENDC3 and TMPyP4, or vehicle controls (DMSO and sterile water, respectively). After 48 hours, total RNA was isolated, quantified, and used in reverse-transcription qPCR to detect differences in RYBP mRNA levels. In all cell lines, samples that were treated with a G4 stabilizing drug were found to express significantly higher levels of RYBP compared to control cells. Our results demonstrate that stabilizing G4 structures increase RYBP transcription, suggesting a regulatory pathway that is readily targetable and worthy of future investigation as a therapeutic application for GBM.