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  • 1
    Keywords: NETWORK ; CDNA ; FUNCTIONAL GENOMICS ; PROTEOMICS ; CDNAS
    Abstract: Among the greatest challenges facing biology today is the exploitation of huge amounts of genomic data, and their conversion into functional information about the proteins encoded. For example, the large-scale cDNA sequencing project of the German cDNA Consortium is providing vast numbers of open reading frames (ORFs) encoding novel proteins of completely unknown function. As a first step towards their characterization we have tagged over 500 of these with the green fluorescent protein (GFP), and examined the subcellular localizations of these fusion proteins in living cells. These data have allowed us to classify the proteins into subcellular groups which determines the next step towards a detailed functional characterization. To make further use of these GFP-tagged constructs, a series of functional assays have been designed and implemented to assess the effect of these novel proteins on processes such as cell growth, cell death, and protein transport. Functional assays with such a large set of molecules is only possible by automation. Therefore, we have developed, and adapted, functional assays for use by robotic liquid handling stations and reading stations. A transport assay allows to identify proteins which localize to distinct organelles of the secretory pathway and have the potential to be new regulators in protein transport, a proliferation assay helps identifying proteins that stimulate or repress mitosis. Further assays to monitor the effects of the proteins in apoptosis and signal transduction pathways are in progress. Integrating the functional information that is generated in the assays with data from expression profiling and further functional genomics and proteomics approaches, will ultimately allow us to identify functional networks of proteins in a morphological context, and will greatly contribute to our understanding of cell function.
    Type of Publication: Journal article published
    PubMed ID: 14649292
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  • 2
    Keywords: CELLS ; CELL ; Germany ; human ; MICROSCOPY ; CLASSIFICATION ; IMAGES ; NETWORKS ; screening ; GENE ; GENES ; GENOME ; PROTEIN ; PROTEINS ; EFFICIENCY ; CULTURED-CELLS ; COMPLEX ; COMPLEXES ; BIOLOGY ; MOLECULAR-BIOLOGY ; IDENTIFICATION ; PATTERNS ; ASSAY ; microarrays ; ARRAYS ; genetics ; REQUIRES ; LOCALIZATION ; Jun ; MORPHOLOGY ; PHENOTYPE ; FUNCTIONAL GENOMICS ; CDNAS ; molecular biology ; molecular ; RE ; PATTERN ; LIGHT ; ARRAY ; genomics ; PATTERN-RECOGNITION ; proteome ; TRANSFECTION
    Abstract: Light microscopic analysis of cell morphology provides a high-content readout of cell function and protein localization. Cell arrays and microwell transfection assays on cultured cells have made cell phenotype analysis accessible to high-through put experiments. Both the localization of each protein in the proteome and the effect of RNAi knock-down of individual genes on cell morphology can be assayed by manual inspection of microscopic images. However, the use of morphological readouts for functional genomics requires fast and automatic identification of complex cellular phenotypes. Here, we present a fully automated platform for high-throughput cell phenotype screening combining human live cell arrays, screening microscopy, and machine-learning-based classification methods. Efficiency of this platform is demonstrated by classification of eleven subcellular patterns marked by GFP-tagged proteins. Our classification method can be adapted to virtually any microscopic assay based on cell morphology, opening a wide range of applications including large-scale RNAi screening in human cells
    Type of Publication: Journal article published
    PubMed ID: 15173118
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  • 3
    Keywords: EXPRESSION ; Germany ; human ; MODEL ; THERAPY ; DIAGNOSIS ; INFORMATION ; NETWORK ; TOOL ; DISEASE ; GENE ; GENES ; GENOME ; PROTEIN ; PROTEINS ; COMPLEX ; COMPLEXES ; BIOLOGY ; SEQUENCE ; FORM ; IDENTIFICATION ; HEALTH ; DATABASE ; PRODUCT ; bioinformatics ; LOCALIZATION ; WEB ; HUMAN GENES ; FUNCTIONAL GENOMICS ; PROTEOMICS ; PRODUCTS ; databases ; ANNOTATION ; RESOURCE ; PROTEIN-ANALYSIS ; FULL-LENGTH HUMAN ; HUMAN CDNAS
    Abstract: As several model genomes have been sequenced, the elucidation of protein function is the next challenge toward the understanding of biological processes in health and disease. We have generated a human ORFeome resource and established a functional genomics and proteomics analysis pipeline to address the major topics in the post-genome-sequencing era: the identification of human genes and splice forms, and the determination of protein localization, activity, and interaction. Combined with the understanding of when and where gene products are expressed in normal and diseased conditions, we create information that is essential for understanding the interplay of genes and proteins in the complex biological network. We have implemented bioinformatics tools and databases that are suitable to store, analyze, and integrate the different types of data from high-throughput experiments and to include further annotation that is based on external information. All information is presented in a Web database (http://www.dkfz.de/LIFEdb). It is exploited for the identification of disease-relevant genes and proteins for diagnosis and therapy
    Type of Publication: Journal article published
    PubMed ID: 15489336
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  • 4
    Keywords: BIOLOGY, CELL, CELLS, COAT, COMPLEX, COMPLEXES, DISSECTION, DYNAMICS, ENDOPLASMIC-RETICULUM, ER exit
    Abstract: The COPII coat complex mediates the formation of transport carriers at specialized sites of the endoplasmic reticulum (ERES). It consists of the Sar1p GTPase and the Sec23/24p and the Sec13/31p subcomplexes [1-3]. Both stimulate the GTPase activity of Sar1p [4], which itself triggers coat disassembly. This built-in GAP activity makes the COPII complex in principle unstable and raises the question of how sufficient stability required for cargo capture and carrier formation is achieved. To address this, we analyzed COPII turnover at single ERES in living cells. The half times for Sar1p, Sec23p, and Sec24p turnover are 1.1, 3.7, and 3.9 s, respectively. Decreasing the amount of transport-competent cargo in the endoplasmic reticulum accelerates turnover of the Sec23/24p and slows down that of Sar1p. A mathematical model of COPII membrane turnover that reproduces the experimental in vivo FRAP kinetics and is consistent with existing in vitro data predicts that Sec23/24p remains membrane associated even after GTP hydrolysis by Sar1p for a duration that is strongly increased by the presence of cargo. We conclude that secretory cargo retains the COPII complex on membranes, after Sar1p release has occurred, and prevents premature disassembly of CON during cargo sorting and transport carrier formation
    Type of Publication: Journal article published
    PubMed ID: 16431369
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  • 5
    Keywords: EXPRESSION ; proliferation ; CELL-PROLIFERATION ; Germany ; INFORMATION ; screening ; GENE ; GENE-EXPRESSION ; GENES ; GENOME ; PROTEIN ; PROTEINS ; gene expression ; ASSAY ; DATABASE ; bioinformatics ; INTERFACE ; PROJECT ; INTEGRATION ; FEATURES ; RE ; cell proliferation ; FULL-LENGTH HUMAN ; HUMAN CDNAS ; ASSAYS ; genomic ; NORTHERN
    Abstract: LIFEdb (http://www.LIFEdb.de) integrates data from large-scale functional genomics assays and manual cDNA annotation with bioinformatics gene expression and protein analysis. New features of LIFEdb include (i) an updated user interface with enhanced query capabilities, (ii) a configurable output table and the option to download search results in XML, (iii) the integration of data from cell-based screening assays addressing the influence of protein-overexpression on cell proliferation and (iv) the display of the relative expression ('Electronic Northern') of the genes under investigation using curated gene expression ontology information. LIFEdb enables researchers to systematically select and characterize genes and proteins of interest, and presents data and information via its user-friendly web-based interface
    Type of Publication: Journal article published
    PubMed ID: 16381901
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  • 6
    Keywords: RECEPTOR ; CELLS ; CELL ; Germany ; screening ; DISEASE ; MORTALITY ; RISK ; GENE ; GENE-EXPRESSION ; GENES ; PROTEIN ; METABOLISM ; BINDING ; BIOLOGY ; TARGET ; ELEMENT ; IDENTIFICATION ; gene expression ; PLASMA ; TRAFFICKING ; MAMMALIAN-CELLS ; cholesterol ; LOW-DENSITY-LIPOPROTEIN ; INSIGHTS ; ER ; CANDIDATE GENES ; regulation ; TECHNOLOGY ; RNAi ; USA ; HOMEOSTASIS ; STRATEGY ; CULTURED FIBROBLASTS
    Abstract: Elevated plasma cholesterol levels are considered responsible for excess cardiovascular morbidity and mortality. Cholesterol in plasma is tightly controlled by cholesterol within cells. Here, we developed and applied an integrative functional genomics strategy that allows systematic identification of regulators of cellular cholesterol levels. Candidate genes were identified by genome-wide gene-expression profiling of sterol-depleted cells and systematic literature queries. The role of these genes in cholesterol regulation was then tested by targeted siRNA knockdown experiments quantifying cellular cholesterol levels and the efficiency of low-density lipoprotein (LDL) uptake. With this strategy, 20 genes were identified as functional regulators of cellular cholesterol homeostasis. Of these, we describe TMEM97 as SREBP target gene that under sterol-depleted conditions localizes to endo-/lysosomal compartments and binds to LDL cholesterol transport-regulating protein Niemann-Pick C1 (NPC1). Taken together, TMEM97 and other factors described here are promising to yield further insights into how cells control cholesterol levels
    Type of Publication: Journal article published
    PubMed ID: 19583955
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  • 7
    Keywords: SIGNAL-TRANSDUCTION ; MAMMALIAN-CELLS ; LIPID RAFTS ; SINGLE-CELL ; reverse transfection ; PROTEIN PALMITOYLATION ; FAMILY KINASES ; CONTENT SCREENING MICROSCOPY ; AUTOMATIC IDENTIFICATION ; COATOMER COMPLEXES
    Abstract: SRC proteins are non-receptor tyrosine kinases that play key roles in regulating signal transduction by a diverse set of cell surface receptors. They contain N-terminal SH4 domains that are modified by fatty acylation and are functioning as membrane anchors. Acylated SH4 domains are both necessary and sufficient to mediate specific targeting of SRC kinases to the inner leaflet of plasma membranes. Intracellular transport of SRC kinases to the plasma membrane depends on microdomains into which SRC kinases partition upon palmitoylation. In the present study, we established a live-cell imaging screening system to identify gene products involved in plasma membrane targeting of SRC kinases. Based on siRNA arrays and a human model cell line expressing two kinds of SH4 reporter molecules, we conducted a genome-wide analysis of SH4-dependent protein targeting using an automated microscopy platform. We identified and validated 54 gene products whose down-regulation causes intracellular retention of SH4 reporter molecules. To detect and quantify this phenotype, we developed a software-based image analysis tool. Among the identified gene products, we found factors involved in lipid metabolism, intracellular transport, and cellular signaling processes. Furthermore, we identified proteins that are either associated with SRC kinases or are related to various known functions of SRC kinases such as other kinases and phosphatases potentially involved in SRC-mediated signal transduction. Finally, we identified gene products whose function is less defined or entirely unknown. Our findings provide a major resource for future studies unraveling the molecular mechanisms that underlie proper targeting of SRC kinases to the inner leaflet of plasma membranes.
    Type of Publication: Journal article published
    PubMed ID: 21795383
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  • 8
    Keywords: COMPLEX ; INFECTION ; IDENTIFICATION ; CORE PROTEIN ; SCREEN ; host factors ; CELLULAR COFACTORS ; HUH-7 CELLS ; PHOSPHATIDYLINOSITOL 4-KINASES ; RNA REPLICATION
    Abstract: Hepatitis C virus (HCV) is a major causative agent of chronic liver disease in humans. To gain insight into host factor requirements for HCV replication, we performed a siRNA screen of the human kinome and identified 13 different kinases, including phosphatidylinositol-4 kinase III alpha (PI4KIIIalpha), as being required for HCV replication. Consistent with elevated levels of the PI4KIIIalpha product phosphatidylinositol-4-phosphate (PI4P) detected in HCV-infected cultured hepatocytes and liver tissue from chronic hepatitis C patients, the enzymatic activity of PI4KIIIalpha was critical for HCV replication. Viral nonstructural protein 5A (NS5A) was found to interact with PI4KIIIalpha and stimulate its kinase activity. The absence of PI4KIIIalpha activity induced a dramatic change in the ultrastructural morphology of the membranous HCV replication complex. Our analysis suggests that the direct activation of a lipid kinase by HCV NS5A contributes critically to the integrity of the membranous viral replication complex.
    Type of Publication: Journal article published
    PubMed ID: 21238945
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  • 9
    Keywords: CELL-MIGRATION ; ACTIN CYTOSKELETON ; EPIDERMAL-GROWTH-FACTOR ; PROTEOMIC ANALYSIS ; TUMOR-SUPPRESSOR ; ALPHA-5-BETA-1 INTEGRIN ; COATED PITS ; RECEPTOR-MEDIATED ENDOCYTOSIS ; MOTOR PROTEINS ; LYSOSOMAL DEGRADATION
    Abstract: alpha2beta1 integrin is one of the most important collagen-binding receptors, and it has been implicated in numerous thrombotic and immune diseases. alpha2beta1 integrin is a potent tumour suppressor, and its downregulation is associated with increased metastasis and poor prognosis in breast cancer. Currently, very little is known about the mechanism that regulates the cell-surface expression and trafficking of alpha2beta1 integrin. Here, using a quantitative fluorescence-microscopy-based RNAi assay, we investigated the impact of 386 cytoskeleton-associated or -regulatory genes on alpha2 integrin endocytosis and found that 122 of these affected the intracellular accumulation of alpha2 integrin. Of these, 83 were found to be putative regulators of alpha2 integrin trafficking and/or expression, with no observed effect on the internalization of epidermal growth factor (EGF) or transferrin. Further interrogation and validation of the siRNA screen revealed a role for KIF15, a microtubule-based molecular motor, as a significant inhibitor of the endocytic trafficking of alpha2 integrin. Our data suggest a novel role for KIF15 in mediating plasma membrane localization of the alternative clathrin adaptor Dab2, thus impinging on pathways that regulate alpha2 integrin internalization.
    Type of Publication: Journal article published
    PubMed ID: 24659801
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  • 10
    Keywords: CANCER ; GROWTH ; INHIBITOR ; proliferation ; SURVIVAL ; tumor ; CELL-PROLIFERATION ; Germany ; KINASE ; INFORMATION ; TOOL ; DISEASE ; GENE ; GENES ; GENOME ; microarray ; PROTEIN ; PROTEINS ; transcription ; TUMORS ; RESOLUTION ; ACTIVATION ; DNA ; BIOLOGY ; cell cycle ; CELL-CYCLE ; CYCLE ; ASSOCIATION ; MOUSE ; IDENTIFICATION ; PROGRESSION ; ASSAY ; microarrays ; PROSTATE-CANCER ; STRATEGIES ; DNA-REPLICATION ; REPLICATION ; signaling ; RE ; TUMORIGENICITY ; genomics ; TRANSITION ; DNA replication ; C-ELEGANS ; cell proliferation ; PROTEIN-ANALYSIS ; development ; ASSAYS ; DIFFERENTIALLY EXPRESSED GENES ; high throughput ; HIGH-THROUGHPUT ; LONG ; PRIME ; PRINCIPLES ; REPRESSOR ; ROLES
    Abstract: Cancer transcription microarray studies commonly deliver long lists of "candidate" genes that are putatively associated with the respective disease. For many of these genes, no functional information, even less their relevance in pathologic conditions, is established as they were identified in large-scale genomics approaches. Strategies and tools are thus needed to distinguish genes and proteins with mere tumor association from those causally related to cancer. Here, we describe a functional profiling approach, where we analyzed 103 previously uncharacterized genes in cancer relevant assays that probed their effects on DNA replication (cell proliferation). The genes had previously been identified as differentially expressed in genome-wide microarray studies of tumors. Using an automated high-throughput assay with single-cell resolution, we discovered seven activators and nine repressors of DNA replication. These were further characterized for effects on extracellular signal-regulated kinase 1/2 (ERK1/2) signaling (G(1)-S transition) and anchorage-independent growth (tumorigenicity). One activator and one inhibitor protein of ERK1/2 activation and three repressors of anchorage-independent growth were identified. Data from tumor and functional profiling make these proteins novel prime candidates for further in-depth study of their roles in cancer development and progression. We have established a novel functional profiling strategy that links genomics to cell biology and showed its potential for discerning cancer relevant modulators of the cell cycle in the candidate lists from microarray studies
    Type of Publication: Journal article published
    PubMed ID: 16140941
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