PhD. Thesis Defense
Candidate: Henry Ochije
Date & Time: Wednesday, June 27, 2018 – 2:00 P.M.
Location: JSNN Auditorium
Major Advisor: Ethan W Taylor, Ph.D.
Title is: “DIFFERENTIAL EFFECT OF ALKALI METAL IONS ON THE STRUCTURE AND STABILITY OF DNA G-QUADRUPLEXES WITH POTENTIAL ROLE IN THE REGULATION OF GENE EXPRESSION”
G-quadruplexes are non-canonical secondary structures formed both in DNA and RNA sequences containing consecutive runs of guanine. Quadruplexes (QPX) can form as an alternate structure in competition with the famous double helix and cells use fluxes of ions, such as sodium and potassium currents in the electrical signals of neurons, to stabilize or destabilize QPX in the nuclei of cells and can play potential role in turning on and off the expression of genes .Previous studies from our lab was conducted using a G-QPX containing region of the promoter of the choline acetyltransferase (ChAT) gene, in driving expression of Green Fluorescent Protein as a “reporter gene”. The transcription factors used to activate the ChAT gene promoter significantly up-regulate the GFP expression Aconitine, a Na+ -channel opening drug. The presence of active transcription factor, led to significant increase in GFP, supporting the idea that monovalent cations have impact on stability / instability of G-QPX (in this case, destabilizing the G-QPX)TMPYP4. TMPYP4 a drug which stabilizes G-QPX formation, was found to significantly decrease GFP expression, suggesting the G-QPX formation is an OFF state for gene expression in this system.A computational study on differential effect of alkali metal ion on the structure of QPX using Na+, Li+ and K+ ions suggests that QPX structures respond to different ion concentration differently and this could be attributed to different structural conformations. This could also be an answer to the divide in literature on the role of lithium in stability of qpx structures. Some are of destabilizing effect while others are of neutral and stabilizing effect. The results also goes to validate the initial result from the lab on ChAT Gene.