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Neelu Puri

Neelu Puri

University of Illinois College of Medicine Rockford, USA

Title: Mechanism of Action of G-quadruplex forming oligonucleotide homologous to the telomere overhang in melanoma

Biography

Neelu Puri has completed her PhD in Biochemistry and Molecular biology from India and postdoctoral training from University of Arizona, Boston University and University of Chicago. She is an Associate professor at University of Illinois at Chicago, Department of Biomedical Sciences Rockford. She has published more than 30 papers in the field of melanoma and lung cancer in reputed international journals.

Abstract

T-oligo, a guanine-rich oligonucleotide (GRO) homologous to the 3’-telomeric overhang of telomeres, elicits potent DNA-damage responses (DDRs) in cancer cells. However, the detailed molecular mechanism of action of T-oligo in cancer cells is largely unknown. Recent studies suggest that GROs can form G-quadruplexes (G4) which are stabilized by the hydrogen-bonding of guanine residues. This study aims to examine the G4-forming capabilities of T-oligo in vitro and comparative analysis of anti-proliferative activities of single-stranded (SS) and G4-T-oligo with investigating the molecular mechanism of T-oligo-induced DDRs in melanoma cells. G4-formation by T-oligo was confirmed using non-denaturing PAGE and NMR. Immunofluorescence study conducted with an anti-G-quadruplex antibody (BG4) showed 88.4% co-localization of T-oligo and BG4 in the nuclei of melanoma cells confirming the ability of T-oligo to form G-quadruplex inside the cells. While G4-T-oligo was found more stable in nuclease degradation assay by DNase I, it has decreased anti-proliferative effects then SS-T-oligo. However, G4-T-oligo has similar cellular uptake as SS-T-oligo. Further, two shelterin complex proteins TRF2 and POT1 were found to be upregulated by T-oligo suggesting TRF2 and POT1 mediated telomere overhang dissociation. Activity of JNK was also upregulated by T-oligo. SP600125 (JNK inhibitor), inhibited T-oligo-mediated JNK-phosphorylation and partially reversed the anti-proliferative activity of T-oligo in melanoma cells. T-oligo also inhibited mRNA expression of hTERT, a catalytic subunit of telomerase. In conclusion, these studies demonstrate that T-oligo can form G-quadruplex and the anti-proliferative mechanism of T-oligo may be mediated through POT1 and TRF2 as well as via JNK-activation inducing hTERT-inhibition in melanoma cells.