DNA Aptamer selection and cellular delivery for the inhibition of E3 Ubiquitin Ligase WWP1

Abstract

The Nedd4 family ubiquitin ligase WWP1 is known to complex with Schnurri3 and polyubiquitinate Runx2, a key transcriptional factor associated with osteoblast differentiation. Runx2 is therefore directed to the proteosome, making WWP1 and Schnurri3 negative regulators of Runx2 and osteoblast differentiation. The disruption of this complex could impede the polyubiquitination of Runx2, causing an increase in osteoblast growth and thus stronger bone in patients suffering from osteoporosis. Three truncations of WWP1 have been cloned into expression vectors, expressed in E. coli, and purified using poly-Histidine tag chromatography. DNA aptamers were then selected against WWP1 using the established SELEX method. Pools of selected aptamers were characterized for homogeneity with DNA sequencing and several groups of enriched and identical DNA sequences were obtained. These enriched sequences are being assesed for their ability to bind the key functional N-lobe region of WWP1 and inhibit its ubiquitination activity with Isothermal Titration Calorimetry and an inhibition assay, repectively. Chosen aptamers will then be conjugated to PTH peptide, which is known to be internalized by osteoblastic cells, in view of delivery to cells in an In Vitro model. This work should lay a foundation for the unmet need of an improved osteoporosis therapy in the future, and a novel approach to treating bone disease.