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  1. Article: Unique folding of precursor microRNAs: quantitative evidence and implications for de novo identification.

    Ng Kwang Loong, Stanley / Mishra, Santosh K

    RNA (New York, N.Y.)

    2007  Volume 13, Issue 2, Page(s) 170–187

    Abstract: MicroRNAs (miRNAs) participate in diverse cellular and physiological processes through the post-transcriptional gene regulatory pathway. Hairpin is a crucial structural feature for the computational identification of precursor miRNAs (pre-miRs), as its ... ...

    Abstract MicroRNAs (miRNAs) participate in diverse cellular and physiological processes through the post-transcriptional gene regulatory pathway. Hairpin is a crucial structural feature for the computational identification of precursor miRNAs (pre-miRs), as its formation is critically associated with the early stages of the mature miRNA biogenesis. Our incomplete knowledge about the number of miRNAs present in the genomes of vertebrates, worms, plants, and even viruses necessitates thorough understanding of their sequence motifs, hairpin structural characteristics, and topological descriptors. In this in-depth study, we investigate a comprehensive and heterogeneous collection of 2241 published (nonredundant) pre-miRs across 41 species (miRBase 8.2), 8494 pseudohairpins extracted from the human RefSeq genes, 12,387 (nonredundant) ncRNAs spanning 457 types (Rfam 7.0), 31 full-length mRNAs randomly selected from GenBank, and four sets of synthetically generated genomic background corresponding to each of the native RNA sequence. Our large-scale characterization analysis reveals that pre-miRs are significantly different from other types of ncRNAs, pseudohairpins, mRNAs, and genomic background according to the nonparametric Kruskal-Wallis ANOVA (p<0.001). We examine the intrinsic and global features at the sequence, structural, and topological levels including %G+C content, normalized base-pairing propensity P(S), normalized minimum free energy of folding MFE(s), normalized Shannon entropy Q(s), normalized base-pair distance D(s), and degree of compactness F(S), as well as their corresponding Z scores of P(S), MFE(s), Q(s), D(s), and F(S). The findings will promote more accurate guidelines and distinctive criteria for the prediction of novel pre-miRs with improved performance.
    MeSH term(s) Animals ; Humans ; MicroRNAs/chemistry ; MicroRNAs/genetics ; MicroRNAs/metabolism ; Nucleic Acid Conformation ; RNA Precursors/chemistry ; RNA Processing, Post-Transcriptional ; RNA, Messenger/chemistry ; RNA, Plant/chemistry ; RNA, Plant/genetics ; RNA, Plant/metabolism ; RNA, Untranslated/chemistry ; RNA, Untranslated/genetics ; RNA, Untranslated/metabolism
    Chemical Substances MicroRNAs ; RNA Precursors ; RNA, Messenger ; RNA, Plant ; RNA, Untranslated
    Language English
    Publishing date 2007-02
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1241540-6
    ISSN 1355-8382
    ISSN 1355-8382
    DOI 10.1261/rna.223807
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: De novo SVM classification of precursor microRNAs from genomic pseudo hairpins using global and intrinsic folding measures.

    Ng, Kwang Loong Stanley / Mishra, Santosh K

    Bioinformatics (Oxford, England)

    2007  Volume 23, Issue 11, Page(s) 1321–1330

    Abstract: ... sg/~stanley/Publications ...

    Abstract Motivation: MicroRNAs (miRNAs) are small ncRNAs participating in diverse cellular and physiological processes through the post-transcriptional gene regulatory pathway. Critically associated with the miRNAs biogenesis, the hairpin structure is a necessary feature for the computational classification of novel precursor miRNAs (pre-miRs). Though many of the abundant genomic inverted repeats (pseudo hairpins) can be filtered computationally, novel species-specific pre-miRs are likely to remain elusive.
    Results: miPred is a de novo Support Vector Machine (SVM) classifier for identifying pre-miRs without relying on phylogenetic conservation. To achieve significantly higher sensitivity and specificity than existing (quasi) de novo predictors, it employs a Gaussian Radial Basis Function kernel (RBF) as a similarity measure for 29 global and intrinsic hairpin folding attributes. They characterize a pre-miR at the dinucleotide sequence, hairpin folding, non-linear statistical thermodynamics and topological levels. Trained on 200 human pre-miRs and 400 pseudo hairpins, miPred achieves 93.50% (5-fold cross-validation accuracy) and 0.9833 (ROC score). Tested on the remaining 123 human pre-miRs and 246 pseudo hairpins, it reports 84.55% (sensitivity), 97.97% (specificity) and 93.50% (accuracy). Validated onto 1918 pre-miRs across 40 non-human species and 3836 pseudo hairpins, it yields 87.65% (92.08%), 97.75% (97.42%) and 94.38% (95.64%) for the mean (overall) sensitivity, specificity and accuracy. Notably, A.mellifera, A.geoffroyi, C.familiaris, E.Barr, H. Simplex virus, H.cytomegalovirus, O.aries, P.patens, R.lymphocryptovirus, Simian virus and Z.mays are unambiguously classified with 100.00% (sensitivity) and >93.75% (specificity).
    Availability: Data sets, raw statistical results and source codes are available at http://web.bii.a-star.edu.sg/~stanley/Publications
    MeSH term(s) Algorithms ; Artificial Intelligence ; Base Sequence ; Chromosome Mapping/methods ; Computer Simulation ; Humans ; MicroRNAs/chemistry ; MicroRNAs/genetics ; MicroRNAs/ultrastructure ; Models, Chemical ; Models, Molecular ; Molecular Sequence Data ; Nucleic Acid Conformation ; Pattern Recognition, Automated/methods ; RNA Precursors/chemistry ; RNA Precursors/genetics ; RNA Precursors/ultrastructure ; Sequence Alignment/methods ; Sequence Analysis, RNA/methods
    Chemical Substances MicroRNAs ; RNA Precursors
    Language English
    Publishing date 2007-06-01
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1422668-6
    ISSN 1367-4811 ; 1367-4803
    ISSN (online) 1367-4811
    ISSN 1367-4803
    DOI 10.1093/bioinformatics/btm026
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Enhanced production of neuroprogenitors, dopaminergic neurons, and identification of target genes by overexpression of sonic hedgehog in human embryonic stem cells.

    Wu, Selena Meiyun / Tan, Ker Sin / Chen, Huishan / Beh, Thian Thian / Yeo, Hock Chuan / Ng, Stanley Kwang-Loong / Wei, Shunhui / Lee, Dong-Yup / Choo, Andre Boon-Hwa / Chan, Ken Kwok-Keung

    Stem cells and development

    2012  Volume 21, Issue 5, Page(s) 729–741

    Abstract: Molecular and cellular signaling pathways are involved in the process of neural differentiation from human embryonic stem cells (hESC) to terminally differentiated neurons. The Sonic hedgehog (SHH) morphogen is required to direct the differentiation of ... ...

    Abstract Molecular and cellular signaling pathways are involved in the process of neural differentiation from human embryonic stem cells (hESC) to terminally differentiated neurons. The Sonic hedgehog (SHH) morphogen is required to direct the differentiation of hESC to several neural subtypes, for example, dopaminergic (DA) or motor neurons. However, the roles of SHH signaling and the pathway target genes that regulate the diversity of cellular responses arising from SHH activation during neurogenesis of hESC have yet to be elucidated. In this study, we report that overexpression of SHH in hESC promotes the derivation of neuroprogenitors (NP), increases proliferation of NP, and subsequently increases the yield of DA neurons. Next, gene expression changes resulting from the overexpression of SHH in hESC-derived NP were examined by genome-wide transcriptional profiling. Categorizing the differentially expressed genes according to the Gene Ontology biological processes showed that they are involved in numerous cellular processes, including neural development, NP proliferation, and neural specification. In silico GLI-binding sites analysis of the differentially expressed genes also identified a set of putative novel direct target genes of SHH in hESC-derived NP, which are involved in nervous system development. Electrophoretic mobility shift assays and promoter-luciferase assays confirmed that GLI1 binds to the promoter region and activates transcription of HEY2, a NOTCH signaling target gene. Taken together, our data provide evidence for the first time that there is cross-talk between the NOTCH and SHH signaling pathways in hESC-derived NP and also provide significant new insights into transcriptional targets in SHH-mediated neural differentiation of hESC.
    MeSH term(s) Basic Helix-Loop-Helix Transcription Factors/genetics ; Basic Helix-Loop-Helix Transcription Factors/metabolism ; Blotting, Western ; Cell Differentiation/genetics ; Cell Line ; Dopaminergic Neurons/cytology ; Dopaminergic Neurons/metabolism ; Dopaminergic Neurons/physiology ; Embryonic Stem Cells/cytology ; Embryonic Stem Cells/metabolism ; Eye Proteins/genetics ; Eye Proteins/metabolism ; Fluorescent Antibody Technique ; Gene Expression Profiling ; Glial Fibrillary Acidic Protein/genetics ; Glial Fibrillary Acidic Protein/metabolism ; Hedgehog Proteins/genetics ; Hedgehog Proteins/metabolism ; Homeodomain Proteins/genetics ; Homeodomain Proteins/metabolism ; Humans ; Intermediate Filament Proteins/genetics ; Intermediate Filament Proteins/metabolism ; Membrane Potentials ; Nerve Tissue Proteins/genetics ; Nerve Tissue Proteins/metabolism ; Nestin ; Neural Stem Cells/cytology ; Neural Stem Cells/metabolism ; Neural Stem Cells/physiology ; PAX6 Transcription Factor ; Paired Box Transcription Factors/genetics ; Paired Box Transcription Factors/metabolism ; Patch-Clamp Techniques ; Promoter Regions, Genetic/genetics ; Protein Binding ; Repressor Proteins/genetics ; Repressor Proteins/metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Transcription Factors/genetics ; Transcription Factors/metabolism ; Zinc Finger Protein GLI1
    Chemical Substances Basic Helix-Loop-Helix Transcription Factors ; Eye Proteins ; GLI1 protein, human ; Glial Fibrillary Acidic Protein ; HEY2 protein, human ; Hedgehog Proteins ; Homeodomain Proteins ; Intermediate Filament Proteins ; NES protein, human ; Nerve Tissue Proteins ; Nestin ; PAX6 Transcription Factor ; PAX6 protein, human ; Paired Box Transcription Factors ; Repressor Proteins ; SHH protein, human ; Transcription Factors ; Zinc Finger Protein GLI1
    Language English
    Publishing date 2012-03-20
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2142214-X
    ISSN 1557-8534 ; 1547-3287
    ISSN (online) 1557-8534
    ISSN 1547-3287
    DOI 10.1089/scd.2011.0134
    Database MEDical Literature Analysis and Retrieval System OnLINE

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