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Members of the lysine (K)-specific demethylase 4 (KDM4) A-D family of histone demethylases are dysregulated in several types of cancer. Here, we reveal a previously unrecognized role of KDM4D in the DNA damage response (DDR). We show that the C-terminal region of KDM4D mediates its rapid recruitment to DNA damage sites. Interestingly, this recruitment is independent of the DDR sensor ataxia telangiectasia mutated (ATM), but dependent on poly (ADP-ribose) polymerase 1 (PARP1), which ADP ribosylates KDM4D after damage. We demonstrate that KDM4D is required for efficient phosphorylation of a subset of ATM substrates. We note that KDM4D depletion impairs the DNA damage-induced association of ATM with chromatin, explaining its effect on ATM substrate phosphorylation. Consistent with an upstream role in DDR, KDM4D knockdown disrupts the damage-induced recombinase Rad51 and tumor protein P53 binding protein foci formation. Consequently, the integrity of homology-directed repair and nonhomologous end joining of DNA breaks is impaired in KDM4D-deficient cells. Altogether, our findings implicate KDM4D in DDR, furthering the links between the cancer-relevant networks of epigenetic regulation and genome stability.histone demethylation | chromosome instability | PARylation

These authors contributed equally to this work. SummaryThe amino acid glycine has a well-established role in signalling in the mammalian central nervous system. For example, glycine acts synergistically with the major excitatory neurotransmitter, glutamate, to regulate the in¯ux of ions such as calcium, through N-methyl-D-aspartate (NMDA) receptors. Plants possess NMDAlike receptors, generically referred to as glutamate receptors (GLRs), named on the basis of their presumed ligand, glutamate. Previously, glycine has not been implicated in plant GLR activity or any other aspect of plant signalling. Using transgenic Arabidopsis seedlings expressing aequorin to monitor ligand-mediated changes in the cytosolic concentration of Ca 2 ([Ca 2 ] cyt ), the data presented herein show that glutamate and glycine act synergistically to control ligand-mediated gating of calcium in plants. Glutamate and glycine synergism also regulates hypocotyl elongation. Transient increases in [Ca 2 ] cyt mediated by glutamate and glycine, as well as hypocotyl elongation, were inhibited by 6,7-dinitroquinoxaline-2,3 dione (DNQX), a competitive inhibitor of animal GLRs. Using a multiscale docking algorithm in combination with a molecular model of the ligand-binding domain of plant GLRs, evidence is provided indicating that glycine, and not glutamate, is likely to be the natural ligand for most plant GLR subunits. These ®ndings uncover a hitherto unconsidered role for glycine signalling in plants, and suggest that the synergistic action of glutamate and glycine at NMDA-like receptors predates the divergence of plants and animals.

development, combining different levels of theory to increase accuracy, aiming to connect chemical and molecular changes to macroscopic observables. In this review, we outline biomolecular simulation methods and highlight examples of its application to investigate questions in biology. enzyme, membrane, molecular dynamics, multiscale, protein, QM/MM 1 | INTRODUCTION Biomolecular simulations are now making significant contributions to a wide variety of problems in drug discovery, drug development, biocatalysis, biotechnology, nanotechnology, chemical biology, and medicine. Biomolecular simulation is a rapidly growing field in scale and impact, increasingly demonstrating its worth in understanding mechanisms and analyzing activities, and contributing to the design of drugs and biocatalysts. Physics-based simulations complement experiments in building a molecular-level understanding of biology: They can test hypotheses and interpret and analyze experimental data in terms of interactions at the atomic level. Different types of simulation techniques have been developed, which are applicable to a range of different problems in biomolecular science. Simulations have already shown their worth in helping to analyze how enzymes catalyze biochemical reactions, and how proteins adopt their functional structures, for example, within cell membranes. They contribute to the design of drugs and catalysts, and in understanding the molecular basis of disease. Simulations have played a key role in developing the conceptual framework now at the heart of biomolecular science: that the dynamics of biological molecules is central to their function. Developing methods from chemical physics and computational science will open exciting new opportunities in biomolecular science, including in drug design and development, biotechnology, and biocatalysis. With high-performance computing resources, large-scale atomistic simulations of biological machines such as the ribosome, proton pumps and motors, membrane receptor complexes, and even whole viruses have become possible. Useful simulations of smaller systems can be carried out with desktop resources, thanks to developments allowing, for example, graphics processing units (GPUs) to be used. A particular challenge across the field is the integration of simulations crossing the span of length-and timescales as different types of simulation method are required for different types of problems. 1 Biomolecular systems pose fundamental scientific challenges (e.g., protein folding, enzyme catalysis, gene regulation, disease mechanisms, and antimicrobial resistance) and are at the heart of many advanced technological developments (drug discovery, biotechnology, biocatalysis, biomaterials, and genetic engineering). Biomolecular systems are inherently complex and pose significant challenges in modeling. An essential underlying paradigm is the need to consider biomolecular ensembles and their dynamics, rather than simply static biomolecular structures to understand and predict their behavior and propertie...

Protein structural analysis demonstrates that water molecules are commonly found in the internal cavities of proteins. Analysis of experimental data on the entropies of inorganic crystals suggests that the entropic cost of transferring such a water molecule to a protein cavity will not typically be greater than 7.0 cal/mol/K per water molecule, corresponding to a contribution of approximately +2.0 kcal/mol to the free energy. In this study, we employ the statistical mechanical method of inhomogeneous fluid solvation theory to quantify the enthalpic and entropic contributions of individual water molecules in 19 protein cavities across five different proteins. We utilize information theory to develop a rigorous estimate of the total two-particle entropy, yielding a complete framework to calculate hydration free energies. We show that predictions from inhomogeneous fluid solvation theory are in excellent agreement with predictions from free energy perturbation (FEP) and that these predictions are consistent with experimental estimates. However, the results suggest that water molecules in protein cavities containing charged residues may be subject to entropy changes that contribute more than +2.0 kcal/mol to the free energy. In all cases, these unfavorable entropy changes are predicted to be dominated by highly favorable enthalpy changes. These findings are relevant to the study of bridging water molecules at protein-protein interfaces as well as in complexes with cognate ligands and small-molecule inhibitors.

Protein-protein interactions (PPIs) underlie the majority of biological processes, signaling, and disease. Approaches to modulate PPIs with small molecules have therefore attracted increasing interest over the past decade. However, there are a number of challenges inherent in developing small-molecule PPI inhibitors that have prevented these approaches from reaching their full potential. From target validation to small-molecule screening and lead optimization, identifying therapeutically relevant PPIs that can be successfully modulated by small molecules is not a simple task. Following the recent review by Arkin et al., which summarized the lessons learnt from prior successes, we focus in this article on the specific challenges of developing PPI inhibitors and detail the recent advances in chemistry, biology, and computation that facilitate overcoming them. We conclude by providing a perspective on the field and outlining four innovations that we see as key enabling steps for successful development of small-molecule inhibitors targeting PPIs.

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr 1 ]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein. 468 Read et al. Receptor residues implicated in apelin binding by mutagenesis. b Receptor residues affecting bias and internalization by mutagenesis. 470 Read et al.

Traditionally a pursuit of large pharmaceutical companies, high-throughput screening assays are becoming increasingly common within academic and government laboratories. This shift has been instrumental in enabling projects that have not been commercially viable, such as chemical probe discovery and screening against high risk targets. Once an assay has been prepared and validated, it must be fed with screening compounds. Crafting a successful collection of small molecules for screening poses a significant challenge. An optimized collection will minimize false positives whilst maximizing hit rates of compounds that are amenable to lead generation and optimization. Without due consideration of the relevant protein targets and the downstream screening assays, compound filtering and selection can fail to explore the great extent of chemical diversity and eschew valuable novelty. Herein, we discuss the different factors to be considered and methods that may be employed when assembling a structurally diverse compound screening collection. Rational methods for selecting diverse chemical libraries are essential for their effective use in high-throughput screens. Keywords Drug-like Molecule:A molecule with molecular properties that overlap with the majority of existing drugs.; High-throughput Screening: A screening process that utilises robotics and rapid data processing to perform millions of assays in a short space of time.; Molecular Similarity: A measure of the relatedness of two molecules. This would ideally quantify the similarity in biological effect but in practice tends to quantify the similarity in structure.; Molecular Diversity: A measure of how well a subset of molecules represents a larger set of molecules. A more diverse subset will tend to have a lower molecular similarity between molecules.; Frequent Hitter: A molecule or molecular substructure that hits numerous screening assays on different drug targets with a mode of action that is assumed to be non-specific.; Substructure Filter: A computational filter used to remove molecules containing molecular substructures that are considered to give rise to non-specific binding or deleterious pharmacodynamic properties.