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Recent Publications

Oncogenic Activation of the RNA Binding Protein NELFE and MYC Signaling in Hepatocellular Carcinoma.

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Oncogenic Activation of the RNA Binding Protein NELFE and MYC Signaling in Hepatocellular Carcinoma.

Cancer Cell. 2017 Jul 10;32(1):101-114.e8

Authors: Dang H, Takai A, Forgues M, Pomyen Y, Mou H, Xue W, Ray D, Ha KCH, Morris QD, Hughes TR, Wang XW

Abstract
Global transcriptomic imbalance is a ubiquitous feature associated with cancer, including hepatocellular carcinoma (HCC). Analyses of 1,225 clinical HCC samples revealed that a large numbers of RNA binding proteins (RBPs) are dysregulated and that RBP dysregulation is associated with poor prognosis. We further identified that oncogenic activation of a top candidate RBP, negative elongation factor E (NELFE), via somatic copy-number alterations enhanced MYC signaling and promoted HCC progression. Interestingly, NELFE induces a unique tumor transcriptome by selectively regulating MYC-associated genes. Thus, our results revealed NELFE as an oncogenic protein that may contribute to transcriptome imbalance in HCC through the regulation of MYC signaling.

PMID: 28697339 [PubMed - indexed for MEDLINE]



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Tracing the origins of relapse in acute myeloid leukaemia to stem cells.

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Tracing the origins of relapse in acute myeloid leukaemia to stem cells.

Nature. 2017 07 06;547(7661):104-108

Authors: Shlush LI, Mitchell A, Heisler L, Abelson S, Ng SWK, Trotman-Grant A, Medeiros JJF, Rao-Bhatia A, Jaciw-Zurakowsky I, Marke R, McLeod JL, Doedens M, Bader G, Voisin V, Xu C, McPherson JD, Hudson TJ, Wang JCY, Minden MD, Dick JE

Abstract
In acute myeloid leukaemia, long-term survival is poor as most patients relapse despite achieving remission. Historically, the failure of therapy has been thought to be due to mutations that produce drug resistance, possibly arising as a consequence of the mutagenic properties of chemotherapy drugs. However, other lines of evidence have pointed to the pre-existence of drug-resistant cells. For example, deep sequencing of paired diagnosis and relapse acute myeloid leukaemia samples has provided direct evidence that relapse in some cases is generated from minor genetic subclones present at diagnosis that survive chemotherapy, suggesting that resistant cells are generated by evolutionary processes before treatment and are selected by therapy. Nevertheless, the mechanisms of therapy failure and capacity for leukaemic regeneration remain obscure, as sequence analysis alone does not provide insight into the cell types that are fated to drive relapse. Although leukaemia stem cells have been linked to relapse owing to their dormancy and self-renewal properties, and leukaemia stem cell gene expression signatures are highly predictive of therapy failure, experimental studies have been primarily correlative and a role for leukaemia stem cells in acute myeloid leukaemia relapse has not been directly proved. Here, through combined genetic and functional analysis of purified subpopulations and xenografts from paired diagnosis/relapse samples, we identify therapy-resistant cells already present at diagnosis and two major patterns of relapse. In some cases, relapse originated from rare leukaemia stem cells with a haematopoietic stem/progenitor cell phenotype, while in other instances relapse developed from larger subclones of immunophenotypically committed leukaemia cells that retained strong stemness transcriptional signatures. The identification of distinct patterns of relapse should lead to improved methods for disease management and monitoring in acute myeloid leukaemia. Moreover, the shared functional and transcriptional stemness properties that underlie both cellular origins of relapse emphasize the importance of developing new therapeutic approaches that target stemness to prevent relapse.

PMID: 28658204 [PubMed - indexed for MEDLINE]



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Evaluation and Design of Genome-Wide CRISPR/SpCas9 Knockout Screens.

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Evaluation and Design of Genome-Wide CRISPR/SpCas9 Knockout Screens.

G3 (Bethesda). 2017 Aug 07;7(8):2719-2727

Authors: Hart T, Tong AHY, Chan K, Van Leeuwen J, Seetharaman A, Aregger M, Chandrashekhar M, Hustedt N, Seth S, Noonan A, Habsid A, Sizova O, Nedyalkova L, Climie R, Tworzyanski L, Lawson K, Sartori MA, Alibeh S, Tieu D, Masud S, Mero P, Weiss A, Brown KR, Usaj M, Billmann M, Rahman M, Constanzo M, Myers CL, Andrews BJ, Boone C, Durocher D, Moffat J

Abstract
The adaptation of CRISPR/SpCas9 technology to mammalian cell lines is transforming the study of human functional genomics. Pooled libraries of CRISPR guide RNAs (gRNAs) targeting human protein-coding genes and encoded in viral vectors have been used to systematically create gene knockouts in a variety of human cancer and immortalized cell lines, in an effort to identify whether these knockouts cause cellular fitness defects. Previous work has shown that CRISPR screens are more sensitive and specific than pooled-library shRNA screens in similar assays, but currently there exists significant variability across CRISPR library designs and experimental protocols. In this study, we reanalyze 17 genome-scale knockout screens in human cell lines from three research groups, using three different genome-scale gRNA libraries. Using the Bayesian Analysis of Gene Essentiality algorithm to identify essential genes, we refine and expand our previously defined set of human core essential genes from 360 to 684 genes. We use this expanded set of reference core essential genes, CEG2, plus empirical data from six CRISPR knockout screens to guide the design of a sequence-optimized gRNA library, the Toronto KnockOut version 3.0 (TKOv3) library. We then demonstrate the high effectiveness of the library relative to reference sets of essential and nonessential genes, as well as other screens using similar approaches. The optimized TKOv3 library, combined with the CEG2 reference set, provide an efficient, highly optimized platform for performing and assessing gene knockout screens in human cell lines.

PMID: 28655737 [PubMed - in process]



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RNAcompete-S: Combined RNA sequence/structure preferences for RNA binding proteins derived from a single-step in vitro selection.

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RNAcompete-S: Combined RNA sequence/structure preferences for RNA binding proteins derived from a single-step in vitro selection.

Methods. 2017 Aug 15;126:18-28

Authors: Cook KB, Vembu S, Ha KCH, Zheng H, Laverty KU, Hughes TR, Ray D, Morris QD

Abstract
RNA-binding proteins recognize RNA sequences and structures, but there is currently no systematic and accurate method to derive large (>12base) motifs de novo that reflect a combination of intrinsic preference to both sequence and structure. To address this absence, we introduce RNAcompete-S, which couples a single-step competitive binding reaction with an excess of random RNA 40-mers to a custom computational pipeline for interrogation of the bound RNA sequences and derivation of SSMs (Sequence and Structure Models). RNAcompete-S confirms that HuR, QKI, and SRSF1 prefer binding sites that are single stranded, and recapitulates known 8-10bp sequence and structure preferences for Vts1p and RBMY. We also derive an 18-base long SSM for Drosophila SLBP, which to our knowledge has not been previously determined by selections from pure random sequence, and accurately discriminates human replication-dependent histone mRNAs. Thus, RNAcompete-S enables accurate identification of large, intrinsic sequence-structure specificities with a uniform assay.

PMID: 28651966 [PubMed - in process]



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Recent advances in understanding contextual TGFβ signaling.

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Recent advances in understanding contextual TGFβ signaling.

F1000Res. 2017;6:749

Authors: Ayyaz A, Attisano L, Wrana JL

Abstract
The appearance of the first animal species on earth coincides with the emergence of transforming growth factor β (TGFβ) pathways. The evolution of these animals into more complex organisms coincides with a progressively increased TGFβ repertoire through gene duplications and divergence, making secreted TGFβ molecules the largest family of morphogenetic proteins in humans. It is therefore not surprising that TGFβ pathways govern numerous aspects of human biology from early embryonic development to regeneration, hematopoiesis, neurogenesis, and immunity. Such heavy reliance on these pathways is reflected in the susceptibility to minor perturbations in pathway components that can lead to dysregulated signaling and a diverse range of human pathologies such as cancer, fibrosis, and developmental disorders. Attempts to comprehensively resolve these signaling cascades are complicated by the long-recognized paradoxical role the pathway plays in cell biology. Recently, several groups have probed examples of the disparate aspects of TGFβ biology in a variety of animal models and uncovered novel context-dependent regulatory mechanisms. Here, we briefly review recent advancements and discuss their overall impact in directing future TGFβ research.

PMID: 28649369 [PubMed]



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Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping.

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Effectively infinite optical path-length created using a simple cubic photonic crystal for extreme light trapping.

Sci Rep. 2017 Jun 23;7(1):4171

Authors: Frey BJ, Kuang P, Hsieh ML, Jiang JH, John S, Lin SY

Abstract
A 900 nm thick TiO2 simple cubic photonic crystal with lattice constant 450 nm was fabricated and used to experimentally validate a newly-discovered mechanism for extreme light-bending. Absorption enhancement was observed extending 1-2 orders of magnitude over that of a reference TiO2 film. Several enhancement peaks in the region from 600-950 nm were identified, which far exceed both the ergodic fundamental limit and the limit based on surface-gratings, with some peaks exceeding 100 times enhancement. These results are attributed to radically sharp refraction where the optical path length approaches infinity due to the Poynting vector lying nearly parallel to the photonic crystal interface. The observed phenomena follow directly from the simple cubic symmetry of the photonic crystal, and can be achieved by integrating the light-trapping architecture into the absorbing volume. These results are not dependent on the material used, and can be applied to any future light trapping applications such as phosphor-converted white light generation, water-splitting, or thin-film solar cells, where increased response in areas of weak absorption is desired.

PMID: 28646167 [PubMed - in process]



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Three-Dimensional Imaging of Transparent Tissues via Metal Nanoparticle Labeling.

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Three-Dimensional Imaging of Transparent Tissues via Metal Nanoparticle Labeling.

J Am Chem Soc. 2017 Jul 26;139(29):9961-9971

Authors: Syed AM, Sindhwani S, Wilhelm S, Kingston BR, Lee DSW, Gommerman JL, Chan WCW

Abstract
Chemical probes are key components of the bioimaging toolbox, as they label biomolecules in cells and tissues. The new challenge in bioimaging is to design chemical probes for three-dimensional (3D) tissue imaging. In this work, we discovered that light scattering of metal nanoparticles can provide 3D imaging contrast in intact and transparent tissues. The nanoparticles can act as a template for the chemical growth of a metal layer to further enhance the scattering signal. The use of chemically grown nanoparticles in whole tissues can amplify the scattering to produce a 1.4 million-fold greater photon yield than obtained using common fluorophores. These probes are non-photobleaching and can be used alongside fluorophores without interference. We demonstrated three distinct biomedical applications: (a) molecular imaging of blood vessels, (b) tracking of nanodrug carriers in tumors, and (c) mapping of lesions and immune cells in a multiple sclerosis mouse model. Our strategy establishes a distinct yet complementary set of imaging probes for understanding disease mechanisms in three dimensions.

PMID: 28641018 [PubMed - in process]



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Hypoxia-Induced Changes in the Fibroblast Secretome, Exosome, and Whole-Cell Proteome Using Cultured, Cardiac-Derived Cells Isolated from Neonatal Mice.

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Hypoxia-Induced Changes in the Fibroblast Secretome, Exosome, and Whole-Cell Proteome Using Cultured, Cardiac-Derived Cells Isolated from Neonatal Mice.

J Proteome Res. 2017 Aug 04;16(8):2836-2847

Authors: Cosme J, Guo H, Hadipour-Lakmehsari S, Emili A, Gramolini AO

Abstract
Cardiac fibroblasts (CFs) represent a major subpopulation of cells in the developing and adult heart. Cardiomyocyte (CM) and CF intercellular communication occurs through paracrine interactions and modulate myocyte development and stress response. Detailed proteomic analysis of the CF secretome in normal and stressed conditions may offer insights into the role of CF in heart development and disease. Primary neonatal mouse CFs were isolated and cultured for 24 h in 21% (normoxic) or 2% (hypoxic) O2. Conditioned medium was separated to obtain exosomes (EXO) and EXO-depleted secretome fractions. Multidimensional protein identification technology was performed on secreted fractions. Whole cell lysate data were also generated to provide subcellular context to the secretome. Proteomic analysis identified 6163 unique proteins in total. Statistical (QSpec) analysis identified 494 proteins differentially expressed between fractions and oxygen conditions. Gene Ontology enrichment analysis revealed hypoxic conditions selectively increase expression of proteins with extracellular matrix and signaling annotations. Finally, we subjected CM pretreated with CF secreted factors to hypoxia/reoxygenation. Viability assays suggested altered viability due to CF-derived factors. CF secretome proteomics revealed differential expression based on mode of secretion and oxygen levels in vitro.

PMID: 28641008 [PubMed - in process]



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The phosphocarrier protein HPr of the bacterial phosphotransferase system globally regulates energy metabolism by directly interacting with multiple enzymes in Escherichia coli.

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The phosphocarrier protein HPr of the bacterial phosphotransferase system globally regulates energy metabolism by directly interacting with multiple enzymes in Escherichia coli.

J Biol Chem. 2017 Aug 25;292(34):14250-14257

Authors: Rodionova IA, Zhang Z, Mehla J, Goodacre N, Babu M, Emili A, Uetz P, Saier MH

Abstract
The histidine-phosphorylatable phosphocarrier protein (HPr) is an essential component of the sugar-transporting phosphotransferase system (PTS) in many bacteria. Recent interactome findings suggested that HPr interacts with several carbohydrate-metabolizing enzymes, but whether HPr plays a regulatory role was unclear. Here, we provide evidence that HPr interacts with a large number of proteins in Escherichia coli We demonstrate HPr-dependent allosteric regulation of the activities of pyruvate kinase (PykF, but not PykA), phosphofructokinase (PfkB, but not PfkA), glucosamine-6-phosphate deaminase (NagB), and adenylate kinase (Adk). HPr is either phosphorylated on a histidyl residue (HPr-P) or non-phosphorylated (HPr). PykF is activated only by non-phosphorylated HPr, which decreases the PykF Khalf for phosphoenolpyruvate by 10-fold (from 3.5 to 0.36 mm), thus influencing glycolysis. PfkB activation by HPr, but not by HPr-P, resulted from a decrease in the Khalf for fructose-6-P, which likely influences both gluconeogenesis and glycolysis. Moreover, NagB activation by HPr was important for the utilization of amino sugars, and allosteric inhibition of Adk activity by HPr-P, but not by HPr, allows HPr to regulate the cellular energy charge coordinately with glycolysis. These observations suggest that HPr serves as a directly interacting global regulator of carbon and energy metabolism and probably of other physiological processes in enteric bacteria.

PMID: 28634232 [PubMed - indexed for MEDLINE]



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Multiple functions of protein phosphatases in receptor tyrosine kinase signaling revealed by interactome analysis.

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Multiple functions of protein phosphatases in receptor tyrosine kinase signaling revealed by interactome analysis.

Mol Cell Oncol. 2017;4(3):e1297101

Authors: Yao Z, Stagljar I

Abstract
To obtain a global picture of how protein phosphatases are involved in receptor tyrosine kinase (RTK) signaling, we mapped the RTK-phosphatase interactome. Analyses of selected interactions revealed detailed mechanisms of their actions. This study provides new knowledge to better understand cancer development and to identify novel therapeutic targets.

PMID: 28616575 [PubMed]



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