Adam Scott: Fine-tuning the nature of sequence-based disorder in ARF transcription regulation
Abstract: Intrinsically disordered proteins (IDP) are abundant in the transcription factors and signaling proteins of all eukaryotic species. Their importance in regulatory pathways is clear, but understanding their functional roles has proven challenging. To address the relationship between conformation and function in IDPs, we study a family of transcription factors called Auxin Response Factors (ARF) from the plant species Arabidopsis thaliana as a model protein family. The ability for ARFs to activate or repress transcription is determined by the sequence bias of the central intrinsically disordered domain. Transcription activating ARFs tend to be glutamine rich, while transcription repressing ARFs tend to be serine and proline rich, but these domains have never been directly examined. We utilize a combination of fluorescent lifetime methods to directly probe the level of hydration, effective hydrodynamic radius, and rate of conformational exchange in these isolated disordered domains. Our work correlates these biophysical measures of conformation in these central disordered domains to their sequence propensities and experimentally verified roles as activators and repressors. These results represent significant progress toward the understanding of an as-yet unexamined, but vital, domain in the overall function of this family of transcription factors. In addition, this work presents a set of experimental methods to evaluate other families of IDPs and further our understanding of the many bio-signaling pathways of which IDPs play a role.
Katrina Piemonte: Probing dynamics in the multimerization of the auxin signaling web
Abstract: Regulation of plant growth and development by the hormone auxin critically depends on the association network of Auxin Response Factors (ARFs) and Indole Acetic Acid/Aux (IAA) proteins. The intermolecular interactions of these transcription factors complexly regulate the repression or activation of the auxin gene family through dimerization and, as only recently discovered, oligomerization. Both hetero- and homo-multimerization occur through the electrostatic-based association of PB1 domain, generally conserved as a C-terminal domain in both protein families. However, the functional specificity, dynamics, and extent of oligomerization have yet to be defined. To fully explore the structural basis of both interaction specificity and dynamics of hetero- and homo-multimerization, we utilize a combination of gel filtration and protein NMR. We make direct comparisons of both ARF and IAA/Aux proteins (ARF5, ARF7, and IAA12) to specifically examine the affect of sequence changes in domains III and IV as well as the hinge between PB1 faces. This combination of biophysical techniques will provide a more thorough examination of the structure and function of the PB1 domain in the complex roles by which the auxin hormone response is regulated.
This poster also presented work of chemistry major Omar Chaawari ('17).
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