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The c-Jun-NH2-terminal kinases (JNKs) regulate cell death, generally through the direct phosphorylation of both pro- and anti-apoptotic substrates. In this report, we demonstrate an alternate mechanism of JNK-mediated cell death involving the anti-apoptotic protein human apurinic/apyrimidinic endonuclease 1 (APE1). Treatment of cells with a variety of genotoxic stresses enhanced APE1-JNK (all isoforms of JNK1 or JNK2) interaction, specifically in cells undergoing apoptosis. Steady-state APE1 levels were decreased in these cells, in which APE1 is ubiquitinated and degraded in a JNK-dependent manner. Absence of JNKs reduced APE1 ubiquitination and increased its abundance. Mechanistically, the E3 ligase ITCH associates with both APE1 and JNK and is necessary for JNK-dependent APE1 ubiquitination and degradation. Structural models of the JNK-APE1 interaction support the observation of enhanced association of the complex in the presence of ubiquitin. The data together show a mechanism of JNK-mediated cell death by the degradation of APE1 through ITCH. [Display omitted] • The interaction between APE1 and JNK is induced in cells undergoing death • JNK promotes APE1 ubiquitination and degradation • JNK-dependent APE1 ubiquitination is mediated by the E3 ligase ITCH • APE1 degradation facilitates cell death Tabanifar et al. report a mechanism of JNK-mediated cell death. Sustained cellular stress signals lead to increased association of JNK with APE1, a pro-survival protein. This leads to the enhanced ubiquitination and degradation of APE1 in a JNK-dependent manner by the recruitment of ITCH. APE1 degradation facilitates cell death. [ABSTRACT FROM AUTHOR]

Intrinsically disordered proteins (IDPs) play an important role in many diseases. IDPs are a large and important class of proteins; estimated to represent a significant fraction of many genomes. In contrast to protein-protein interactions between well-folded proteins, IDPs typically bind to targets using short consecutive stretches of amino acids. Structures of IDPs complexed with a target have shown great diversity in binding modes. However, how this binding diversity is achieved at the molecular level is not well understood. Unfortunately, the prediction and detailed characterization of IDPs experimentally is still a very challenging task; however molecular mechanics based molecular dynamics simulation are well suited for studying the dynamic behavior of IDPs. We look into the current state for force fields for simulating IDPs and an example of how these methods have been applied to the p53 protein. p53 is one of the most extensively studied IDPs, with multiple intrinsically disordered regulatory domains that mediate its interactions with many other proteins engaged in multiple biological pathways. We show how molecular dynamics simulations can be used to elucidate on the mechanisms involved in selection of the different binding partners. [ABSTRACT FROM AUTHOR]

The PI3K/AKT pathway is the focus of several targeted therapeutic agents for a variety of malignancies. In ERBB2-amplified breast cancer, the hyperactivation of this signaling cascade is associated with resistance to ERBB2-targeted therapy. This can occur through gain-of-function alterations or compensatory mechanisms that enter into play upon pharmacological pressure. The strong rationale in combining anti-ERBB2 agents with PI3K/AKT inhibitors, together with the identification of genomic alterations conferring sensitivity to targeted inhibition, are guiding the design of clinical studies aimed at preventing the emergence of drug resistance and achieving more durable response. In the present review, we describe the involvement of this pathway in breast cancer pathogenesis, with an emphasis on AKT kinases, and provide insight into currently available targeted agents for the treatment of ERBB2-amplified breast cancer. Finally, we provide preliminary data on a novel AKT3 mutation detected in the context of resistance to anti-ERBB2 therapy as an example of genomics-based approaches towards uncovering novel actionable targets in this setting. [ABSTRACT FROM AUTHOR]

Abstract: The term epigenetics is defined as inheritable changes that influence the outcome of a phenotype without changes in the genome. Epigenetics is based upon DNA methylation and posttranslational histone modifications. While there is much known about reversible acetylation as a posttranslational modification, research on reversible histone methylation is still emerging, especially with regard to drug discovery. As aberrant epigenetic modifications have been linked to many diseases, inhibitors of histone modifying enzymes are very much in demand. This article will summarize the progress on small molecule epigenetic inhibitors identified by structure- and computer-based approaches. [Copyright &y& Elsevier]

The tenovins are a frequently studied class of compounds capable of inhibiting sirtuin activity, which is thought to result in increased acetylation and protection of the tumor suppressor p53 from degradation. However, as we and other laboratories have shown previously, certain tenovins are also capable of inhibiting autophagic flux, demonstrating the ability of these compounds to engage with more than one target. In this study, we present two additional mechanisms by which tenovins are able to activate p53 and kill tumor cells in culture. Thesemechanisms are the inhibition of a key enzyme of the de novo pyrimidine synthesis pathway, dihydroorotate dehydrogenase (DHODH), and the blockage of uridine transport into cells. These findings hold a 3- fold significance: first, we demonstrate that tenovins, and perhaps other compounds that activate p53, may activate p53 by more than one mechanism; second, that work previously conducted with certain tenovins as SirT1 inhibitors should additionally be viewed through the lens of DHODH inhibition as this is a major contributor to the mechanism of action of the most widely used tenovins; and finally, that small changes in the structure of a small molecule can lead to a dramatic change in the target profile of the molecule even when the phenotypic readout remains static. [ABSTRACT FROM AUTHOR]

Macrocyclic α-helical peptides have emerged as a compelling new therapeutic modality to tackle targets confined to the intracellular compartment. Within the scope of hydrocarbon-stapling there has been significant progress to date, including the first stapled α-helical peptide to enter into clinical trials. The principal design concept of stapled α-helical peptides is to mimic a cognate (protein) ligand relative to binding its target via an α-helical interface. However, it was the proclivity of such stapled α-helical peptides to exhibit cell permeability and proteolytic stability that underscored their promise as unique macrocyclic peptide drugs for intracellular targets. This perspective highlights key learnings as well as challenges in basic research with respect to structure-based design, innovative chemistry, cell permeability and proteolytic stability that are essential to fulfill the promise of stapled α-helical peptide drug development. [ABSTRACT FROM AUTHOR]

Summary PIK3CA , which encodes the p110α subunit of PI3K, is frequently mutated and oncogenic in breast cancer. PI3Kα inhibitors are in clinical development and despite promising early clinical activity, intrinsic resistance is frequent among patients. We have previously reported that residual downstream mTORC1 activity upon treatment with PI3Kα inhibitors drives resistance to these agents. However, the mechanism underlying this phenotype is not fully understood. Here we show that in cancer cells resistant to PI3Kα inhibition, PDK1 blockade restores sensitivity to these therapies. SGK1, which is activated by PDK1, contributes to the maintenance of residual mTORC1 activity through direct phosphorylation and inhibition of TSC2. Targeting either PDK1 or SGK1 prevents mTORC1 activation, restoring the antitumoral effects of PI3Kα inhibition in resistant cells. [ABSTRACT FROM AUTHOR]

Mutations in the pioneer transcription factor FOXA1 are a hallmark of estrogen receptor-positive (ER+) breast cancers. Examining FOXA1 in ∼5,000 breast cancer patients identifies several hotspot mutations in the Wing2 region and a breast cancer-specific mutation SY242CS, located in the third β strand. Using a clinico-genomically curated cohort, together with breast cancer models, we find that FOXA1 mutations associate with a lower response to aromatase inhibitors. Mechanistically, Wing2 mutations display increased chromatin binding at ER loci upon estrogen stimulation, and an enhanced ER-mediated transcription without changes in chromatin accessibility. In contrast, SY242CS shows neomorphic properties that include the ability to open distinct chromatin regions and activate an alternative cistrome and transcriptome. Structural modeling predicts that SY242CS confers a conformational change that mediates stable binding to a non-canonical DNA motif. Taken together, our results provide insights into how FOXA1 mutations perturb its function to dictate cancer progression and therapeutic response. • FOXA1 mutations are enriched in metastatic tumors • FOXA1 mutations are associated with worse outcome to aromatase inhibitors • Wing2 mutations promote an enhanced estrogen response upon estrogen • SY242CS induces alternative chromatin states by binding to a non-canonical motif Arruabarrena-Aristorena et al. determine that mutations in the pioneer transcription factor FOXA1 lower the therapeutic response to aromatase inhibitors in ER+ breast cancer. Mechanistically, two phenotypic groups are established: hypermorphic Wing2 mutants that augment estrogen response, and a neomorphic SY242CS mutant that promotes an alternative pioneering, and cistromic and transcriptomic function. [ABSTRACT FROM AUTHOR]