Hdm2 (human MDM2, human double minute 2 homologue) counteracts p53 function by direct binding to p53 and by ubiquitin‐dependent p53 protein degradation. Activation of p53 by inhibitors of the p53–Hdm2 interaction is being pursued as a therapeutic strategy in p53 wild‐type cancers. In addition, HdmX (human MDMX, human MDM4) was also identified as an important therapeutic target to efficiently reactivate p53, and it is likely that dual inhibition of Hdm2 and HdmX is beneficial. Herein we report four new X‐ray structures for Hdm2 and five new X‐ray structures for HdmX complexes, involving different classes of synthetic compounds (including the worldwide highest resolutions for Hdm2 and HdmX, at 1.13 and 1.20 Å, respectively). We also reveal the key additive 18‐crown‐ether, which we discovered to enable HdmX crystallization and show its stabilization of various Lys residues. In addition, we report the previously unpublished details of X‐ray structure determinations for eight further Hdm2 complexes, including the clinical trial compounds NVP‐CGM097 and NVP‐HDM201. An analysis of all compound binding modes reveals new and deepened insight into the possible adaptations and structural states of Hdm2 (e.g., flip of F55, flip of Y67, reorientation of H96) and HdmX (e.g., flip of H55, dimer induction), enabling key binding interactions for different compound classes. To facilitate comparisons, we used the same numbering for Hdm2 (as in Q00987) and HdmX (as in O15151, but minus 1). Taken together, these structural insights should prove useful for the design and optimization of further selective and/or dual Hdm2/HdmX inhibitors.
The transcription factor PAX8 is critical for the development of the thyroid and urogenital system. Comprehensive genomic screens furthermore indicate an additional oncogenic role for PAX8 in renal and ovarian cancers. While a plethora of PAX8-regulated genes in different contexts have been proposed, we still lack a mechanistic understanding of how PAX8 engages molecular complexes to drive disease-relevant oncogenic transcriptional programs. Here we show that protein isoforms originating from the MECOM locus form a complex with PAX8. These include MDS1-EVI1 (also called PRDM3) for which we map its interaction with PAX8 in vitro and in vivo. We show that PAX8 binds a large number of genomic sites and forms transcriptional hubs. At a subset of these, PAX8 together with PRDM3 regulates a specific gene expression module involved in adhesion and extracellular matrix. This gene module correlates with PAX8 and MECOM expression in large scale profiling of cell lines, patient-derived xenografts (PDXs) and clinical cases and stratifies gynecological cancer cases with worse prognosis. PRDM3 is amplified in ovarian cancers and we show that the MECOM locus and PAX8 sustain in vivo tumor growth, further supporting that the identified function of the MECOM locus underlies PAX8-driven oncogenic functions in ovarian cancer.
In this study, we describe the rapid identification of potent binders for the WD40 repeat domain (WDR) of DCAF1. This was achieved by two rounds of iterative focused screening of a small set of compounds selected on the basis of internal WDR domain knowledge followed by hit expansion. Subsequent structure-based design led to nanomolar potency binders with a clear exit vector enabling DCAF1-based bifunctional degrader exploration.
The Front Cover shows a crystal of HdmX in a drop of mother liquor and the X‐ray structures of the clinical trial compounds NVP‐CGM097 and NVP‐HDM201 bound to Hdm2. The article reveals key structural states of the cancer target proteins Hdm2 and HdmX. Elucidation of the binding interactions for different chemical classes of inhibitors and of the sometimes surprising protein adaptations was key in the design and optimization of these inhibitors. For HdmX, a key crystallization additive is revealed, which enabled the determination of high‐resolution structures. Taken together, these new X‐ray findings (nine new structures for Hdm2, HdmX, and the previously unpublished details for eight Hdm2 complexes) should prove to be useful for the design and optimization of further selective or dual inhibitors. More information can be found in the Communication by Joerg Kallen, Pascal Furet et al. on page 1305 in Issue 14, 2015 (DOI: 10.1002/cmdc.201900201).
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