Transcriptional and Post-Transcriptional Control of Therapeutic Gene Expression during Disease Activity

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease which predominantly affects the synovial joints. Local gene therapy represents an approach to produce therapeuticmolecules (i.e. soluble TNF receptor (sTNFR)-Fc and interleukin-1 receptor antagonist (IL-1Ra)) directly in arthritic joints. Gene therapy could be designed to link the level of therapeutic gene expression directly to disease activity, through the use of transcriptional and posttranscriptional regulatory elements. The experiments in this thesis describe the construction of multi-responsive, composite synthetic promoters, comprised of the binding sites for an array of transcription factors activated in arthritic joints. Optimal spatial arrangements of binding sites in relation to each other and to the TATA box were determined by Assembly PCR cloning and the functionality of the resulting synthetic promoters revealed additive or synergistic induction of luciferase reporter gene expression in response to combined stimulation. Candidate synthetic promoters were cloned into a lentiviral vector between insulator elements and displayed significantly enhanced induction, in excess of 1,500 fold in response to combined stimulation. Inflammation-specific activation of lentiviral synthetic promoters was confirmed in a carrageenan-induced paw inflammation mouse model, which demonstrated the strong correlation between local luciferase gene expression and paw inflammation. Post-transcriptional gene regulation was also investigated by exploiting the differential expression of endogenous miR-23b during inflammation. Insertion of miR-23b target sites into the 3’UTR of the luciferase gene subjected luciferase mRNA to regulation by miR-23b. Experiments demonstrated that high basal gene expression driven by constitutive and inducible promoters was significantly downregulated by miR-23b without significantly impairing high gene expression upon stimulation. Overall, the experiments in this thesis have confirmed the induction of inflammation-specific gene expression, regulated by inflammationresponsive endogenous transcriptional and post-transcriptional elements.