Regulation of Ets Transcription Factors
The Ets family of transcription factors and oncoproteins has emerged as a paradigm for the study of the gene expression in eukaryotes. The activities of these proteins are dependent upon numerous possible protein-protein and protein-DNA interactions, thus providing an ideal system for investigating structurally the mechanisms of transcriptional regulation and its relationship to oncogenesis. In particular, we are focusing on the control of murine Ets-1 through auto-inhibition of DNA binding, protein partnerships, and post-translational modifications, including phosphorylation and sumoylation, via signal transduction cascades.
Most significantly, we have developed a model for the allosteric regulation of Ets-1 in which increasing multi-site phosphorylation of a dynamic, unstructured serine rich region leads to a progressive decrease in promoter affinity due to transient interactions that stabilize a labile auto-inhibitory helix appended to the DNA binding ETS domain. This defines a "rheostatic" (rather than off/on) mechanism for cell signaling by fine tuning transcription at the level of DNA binding.
In parallel, we have also undertaken detailed structural and dynamic analyses of the PNT domain from several Ets transcription factors. The Ets-1 PNT domain serves as a docking motif for the MAP kinase ERK2, thereby facilitating phosphorylation of two adjacent phosphoacceptors. These modifications shift a conformational equilibrium of a dynamic helix in the PNT domain from a more closed to a more open state, thereby facilitating binding to the TAZ1 domain of the co-activator CBP. This phospho-switch mechanism also highlights the role of appended dynamic elements to conserved structural domains in the evolution of signalling pathways.