Development of Peptidomimetic Regulators of Myc function

Lead Research Organisation: University of Leeds
Department Name: Sch of Molecular & Cellular Biology


Myc proteins are transcription factors that markedly alter gene expression through both activation and repression of transcription. There are three Myc protein family members in humans (c-Myc, N-Myc, L-Myc), which are all aberrantly expressed in cancers. Inhibition of Myc is a validated therapeutic strategy, but efforts to develop clinical compounds that target Myc proteins directly have failed. c-Myc, N-Myc and L-Myc have regions of sequence homology that mediate interactions with critical partner proteins. The Myc transactivation domain (TAD), is intrinsically disordered, as reported by circular dichroism and NMR spectroscopy, but there are transient secondary structure elements that, in some cases, become stable in complex with binding partners. Several interacting partners of Myc proteins interact in the TAD and mediate transcriptional activation (or repression) functions of Myc, such as WDR5 and CDK9. Other binding partners regulate the ubiquitination and degradation of Myc, such as FbxW7 and Aurora-A. The structure of the complex between N-Myc and Aurora-A, revealed that part of the N-Myc protein folds into a helix that packs against the surface of the kinase. Aurora-A kinase regulates mitotic entry and mitotic spindle assembly and is a promising target for anticancer therapy. The microtubule-associated protein TPX2 activates Aurora-A through binding to two sites, as shown by the X-ray crystal structure of the Aurora-A-TPX2 complex.

In this PhD studentship we will develop peptidomimetic-based inhibitors of key Myc interactions. We will also develop TPX2 peptidomimetics and investigate their binding affinity for Aurora-A. We will exploit state of the art methodology developed to constrain peptides in a bioactive conformation; briefly through reversible reaction of peptides bearing judiciously placed thiol side-chains (Cys/ hCys) with dibromomaleimide. Constrained peptides are considered advantageous in terms of proteolytic/serum stability, enhanced target affinity due to preorganisation and cell-uptake properties. Moreover, we will also exploit this capability in the context of PTMs (e.g. phosphorylation) within the Myc peptides to evaluate the role of order/disorder transitions on the protein-protein interaction network. This will enable functional studies on the interactions, for example to determine the consequences of disruption of the interaction at a specific point in the cell-cycle.

The developed reagents will be used in target validation experiments to probe which of the interactions of Myc are critical for the survival of cancer cells, but dispensible in normal cell types. Beyond the fundamental insight this studentship will deliver on regulation of Myc, Identification of a potential strategy for targeting Myc, represents the first stage in expanding the project into drug discovery.


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