230 research outputs found

    Notch and MAML-1 Complexation Do Not Detectably Alter the DNA Binding Specificity of the Transcription Factor CSL

    Get PDF
    Canonical Notch signaling is initiated when ligand binding induces proteolytic release of the intracellular part of Notch (ICN) from the cell membrane. ICN then travels into the nucleus where it drives the assembly of a transcriptional activation complex containing the DNA-binding transcription factor CSL, ICN, and a specialized co-activator of the Mastermind family. A consensus DNA binding site motif for the CSL protein was previously defined using selection-based methods, but whether subsequent association of Notch and Mastermind-like proteins affects the DNA binding preferences of CSL has not previously been examined.Here, we utilized protein-binding microarrays (PBMs) to compare the binding site preferences of isolated CSL with the preferred binding sites of CSL when bound to the CSL-binding domains of all four different human Notch receptors. Measurements were taken both in the absence and in the presence of Mastermind-like-1 (MAML1). Our data show no detectable difference in the DNA binding site preferences of CSL before and after loading of Notch and MAML1 proteins.These findings support the conclusion that accrual of Notch and MAML1 promote transcriptional activation without dramatically altering the preferred sites of DNA binding, and illustrate the potential of PBMs to analyze the binding site preferences of multiprotein-DNA complexes

    Data Publication with the Structural Biology Data Grid Supports Live Analysis

    Get PDF
    Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data.sbgrid.org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis

    Structural and Atropisomeric Factors Governing the Selectivity of Pyrimido-benzodiazipinones as Inhibitors of Kinases and Bromodomains

    Get PDF
    This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this recordBromodomains have been pursued intensively over the past several years as emerging targets for the devel-opment of anti-cancer and anti-inflammatory agents. It has recently been shown that some kinase inhibitors are able to potently inhibit the bromodomains of BRD4. The clinical activities of PLK inhibitor BI-2536 and JAK2-FLT3 inhibitor TG101348 have been attributed to this unexpected poly-pharmacology, indicating that dual-kinase/bromodomain activity may be advantageous in a therapeutic context. However, for target validation and biological investigation, a more selec-tive target profile is desired. Here we report that benzo[e]pyrimido-[5,4-b]diazepine-6(11H)-ones, versatile ATP-site di-rected kinase pharmacophores utilized in the development of inhibitors of multiple kinases including a number of previ-ously reported kinase chemical probes, are also capable of exhibiting potent BRD4-dependent pharmacology. Using a dual kinase-bromodomain inhibitor of the kinase domains of ERK5 and LRRK2, and the bromodomain of BRD4 as a case study, we define the structure-activity relationships required to achieve dual kinase/BRD4 activity as well as how to di-rect selectivity towards inhibition of either ERK5 or BRD4. This effort resulted in identification of one of the first report-ed kinase-selective chemical probes for ERK5 (JWG-071), a BET selective inhibitor with 1 μM BRD4 IC50 (JWG-115), and additional inhibitors with rationally designed polypharmacology (JWG-047, JWG-069). Co-crystallography of seven representative inhibitors with the first bromodomain of BRD4 demonstrate that distinct atropisomeric conformers rec-ognize the kinase ATP-site and the BRD4 acetyl lysine binding site, conformational preferences supported by rigid dock-ing studies.This work was supported by NIH (Grant No. U54HL127365, to N.S.G. and J.W.; No. NIH P50 GM107618, to X.X. and S.C.B.; Nos. NIH U54 HD093540 and P01 CA066996, to J.Q.), the Medical Research Council (No. MC_UU_12016/2, to D.R.A.), the Spanish Ministerio de Economia y Competitividad (MINECO) (Grant No. SAF2015-60268R, to J.M.L.), and Fondo Europeo de Desarrollo Regional (FEDER) funds (to J.M.L.). D.L.B. was supported as a Merck Fellow of Damon Runyon Cancer Research Foundation (No. DRG-2196-14)

    Effects of S1 Cleavage on the Structure, Surface Export, and Signaling Activity of Human Notch1 and Notch2

    Get PDF
    Notch receptors are normally cleaved during maturation by a furin-like protease at an extracellular site termed S1, creating a heterodimer of non-covalently associated subunits. The S1 site lies within a key negative regulatory region (NRR) of the receptor, which contains three highly conserved Lin12/Notch repeats and a heterodimerization domain (HD) that interact to prevent premature signaling in the absence of ligands. Because the role of S1 cleavage in Notch signaling remains unresolved, we investigated the effect of S1 cleavage on the structure, surface trafficking and ligand-mediated activation of human Notch1 and Notch2, as well as on ligand-independent activation of Notch1 by mutations found in human leukemia.The X-ray structure of the Notch1 NRR after furin cleavage shows little change when compared with that of an engineered Notch1 NRR lacking the S1-cleavage loop. Likewise, NMR studies of the Notch2 HD domain show that the loop containing the S1 site can be removed or cleaved without causing a substantial change in its structure. However, Notch1 and Notch2 receptors engineered to resist S1 cleavage exhibit unexpected differences in surface delivery and signaling competence: S1-resistant Notch1 receptors exhibit decreased, but detectable, surface expression and ligand-mediated receptor activation, whereas S1-resistant Notch2 receptors are fully competent for cell surface delivery and for activation by ligands. Variable dependence on S1 cleavage also extends to T-ALL-associated NRR mutations, as common class 1 mutations display variable decrements in ligand-independent activation when introduced into furin-resistant receptors, whereas a class 2 mutation exhibits increased signaling activity.S1 cleavage has distinct effects on the surface expression of Notch1 and Notch2, but is not generally required for physiologic or pathophysiologic activation of Notch proteins. These findings are consistent with models for receptor activation in which ligand-binding or T-ALL-associated mutations lead to conformational changes of the NRR that permit metalloprotease cleavage

    Data publication with the structural biology data grid supports live analysis

    Get PDF
    Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data. sbgrid. org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis

    Catalytic Mechanism of Bacteriophage T4 Rad50 ATP Hydrolysis

    Get PDF
    Spontaneous double-strand breaks (DSBs) are one of the most deleterious forms of DNA damage, and their improper repair can lead to cellular dysfunction. The Mre11 and Rad50 proteins, a nuclease and an ATPase, respectively, form a well-conserved complex that is involved in the initial processing of DSBs. Here we examine the kinetic and catalytic mechanism of ATP hydrolysis by T4 Rad50 (gp46) in the presence and absence of Mre11 (gp47) and DNA. Single-turnover and pre-steady state kinetics on the wild-type protein indicate that the rate-limiting step for Rad50, the MR complex, and the MR-DNA complex is either chemistry or a conformational change prior to catalysis. Pre-steady state product release kinetics, coupled with viscosity steady state kinetics, also supports that the binding of DNA to the MR complex does not alter the rate-limiting step. The lack of a positive deuterium solvent isotope effect for the wild type and several active site mutants, combined with pH–rate profiles, implies that chemistry is rate-limiting and the ATPase mechanism proceeds via an asymmetric, dissociative-like transition state. Mutation of the Walker A/B and H-loop residues also affects the allosteric communication between Rad50 active sites, suggesting possible routes for cooperativity between the ATP active sites
    corecore