All ETDs from UAB

Advisory Committee Chair

Casey T Weaver

Advisory Committee Members

Robin D Hatton

Christopher A Klug

Etty N Benveniste

Thomas M Ryan

Louis B Justement

Document Type

Dissertation

Date of Award

2010

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

The ability to differentially manipulate available genetic information in order to generate diverse cellular identities represents an innovation of complex multicellular eukaryotic organisms. Cis-acting modules that regulate transcription play extremely important roles in ensuring lineage-specific expression of genes that define cellular identities. In our studies, using Interferon-gamma (IFN-gamma, a cytokine encoded by the gene Ifng), a cytokine encoded by T, NK and NKT cells as a model, we have identified and characterized the roles of key cis regulatory elements that facilitate T lineage specific induction as well as repression of Ifng transcription. In particular, our studies have highlighted the role of RelA, an NF-kappa B family member in driving acute Ifng transcription in response to reactivation signals. These studies have led to the recognition of multiple conserved non-coding sequences (CNS) in the Ifng locus including CNSs -34, -22, +46 and +54 that positively modulate Ifng transcription by co-recruiting STAT4 and RelA. To gain further insight into the actions of these complex cis-regulatory modules in induction of Ifng transcription in vivo, we have generated mice that carry a targeted deletion of a candidate enhancer CNS-22 that has been demonstrated to recruit multiple key trans factors including T-bet, STAT4, Runx3 and RelA to transactivate Ifng transcription. Th1, Tc1 and NK cells derived from CNS-22-/- mice are severely compromised in their ability to secrete IFN-gamma in response to IL-12 and IL-18, but also show less prominent defects in IFN-gamma induction in response to TCR reactivation signals as well. Using CNS-22 as a candidate enhancer, we have also explored some of the fundamental mechanisms that facilitate enhancer actions of CNS-22. Specifically, we demonstrate that activation induced local hyperacetylation of regions that flank CNS-22 plays an essential role in driving inducible transcription of Ifng. Lastly, we extend our findings to other distal enhancers and demonstrate stimulus-responsive activation of Ifng expression is associated with inducible hyperacetylation of local micro-domains that flank multiple enhancers that activate Ifng transcription.

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