G-quadruplex formation in the kRAS mid promoter region and identification of stabilizing small molecules as promising transcriptional silencers

5^th World Congress on Cancer Therapy

September 28-30, 2015 Atlanta, USA

Rhianna K Morgan�?¹, Khondaker Miraz Rahman2, and Tracy A Brooks1

1Department of BioMolecular Sciences, Division of Pharmacology, School of Pharmacy, University of Mississippi, USA
2Institute of Pharmaceutical Sciences, King��?s College, London, England, United Kingdom

Posters-Accepted Abstracts: J Cancer Sci Ther

Abstract :

Over 60% of pancreatic cancers harbor mutations in the kRAS oncogene, whose promoter has three distinct guanine-rich regions (near, mid, and far) capable of forming higher order G-quadruplexes (G4s). These important structures have transcriptional silencing potential and stabilizing compounds cause selective apoptosis in kRAS-addicted cells. Previous works in our laboratory have identified the mid-G4 region as having the highest silencing capacity, with little apparent roles for the near- or far-G4 regions. The structure of this mid-region G4 is being elucidated by electromobility shift assay, DNA polymerase stop assay, DMS footprinting, and circular dichroism (CD). In addition, small molecules are being screened by the F�?¶rster Resonance Energy Transfer (FRET) melt assay and confirmed by CD for their stabilization potential. We have identified multiple, equilibrating, intramolecular G4s forming within the mid-region of the kRAS promoter. Varying buffer conditions (cations, dehydration, and molecular crowding) affect these formations; the predominating isoform is a tetra-stacked mixed parallel and antiparallel structure with an 8:15:7 loop configuration. Over 1,600 compounds have been screened and several are being pursued as leads. Several compounds selectively stabilized the mid-G4 and suppress kRAS transcription. Our work highlights the mid-G4-forming region of the kRAS promoter a therapeutic target with the utmost promise for pancreatic cancer, and further features the stabilizing potential of targeted compounds. Studies are ongoing to vet the potential of other â�?�?hitâ�? compounds from the FRET screen, as well as to elucidate the structure of the kRAS mid-G4 in chromosomal DNA.

Biography :

Rhianna is a current doctoral student at the University of Mississippi with a focus in pharmacology. She has completed her B.A. at the age of 21 years from Hartwick College in mathematics with a minor in biology. As a second year graduate student, she has published two papers, received first place in the Mississippi INBRE Graduate Scholars Symposium, and has been awarded a Graduate Student Council grant from the University of Mississippi.

Email: rhianna.k.morgan@gmail.com