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Articles 1 - 28 of 28
Full-Text Articles in Life Sciences
The Decapping Scavenger Enzyme Dcs-1 Controls Microrna Levels In Caenorhabditis Elegans, Gabriel Bosse, Stefan Ruegger, Maria Ow, Alejandro Vasquez-Rifo, Evelyne Rondeau, Victor Ambros, Helge Grosshans, Martin Simard
The Decapping Scavenger Enzyme Dcs-1 Controls Microrna Levels In Caenorhabditis Elegans, Gabriel Bosse, Stefan Ruegger, Maria Ow, Alejandro Vasquez-Rifo, Evelyne Rondeau, Victor Ambros, Helge Grosshans, Martin Simard
Victor R. Ambros
In metazoans, microRNAs play a critical role in the posttranscriptional regulation of genes required for cell proliferation and differentiation. MicroRNAs themselves are regulated by a multitude of mechanisms influencing their transcription and posttranscriptional maturation. However, there is only sparse knowledge on pathways regulating the mature, functional form of microRNA. Here, we uncover the implication of the decapping scavenger protein DCS-1 in the control of microRNA turnover. In Caenorhabditis elegans, mutations in dcs-1 increase the levels of functional microRNAs. We demonstrate that DCS-1 interacts with the exonuclease XRN-1 to promote microRNA degradation in an independent manner from its known decapping scavenger …
Developmental Decline In Neuronal Regeneration By The Progressive Change Of Two Intrinsic Timers, Yan Zou, Hui Chiu, Anna Zinovyeva, Victor Ambros, Chiou-Fen Chuang, Chieh Chang
Developmental Decline In Neuronal Regeneration By The Progressive Change Of Two Intrinsic Timers, Yan Zou, Hui Chiu, Anna Zinovyeva, Victor Ambros, Chiou-Fen Chuang, Chieh Chang
Victor R. Ambros
Like mammalian neurons, Caenorhabditis elegans neurons lose axon regeneration ability as they age, but it is not known why. Here, we report that let-7 contributes to a developmental decline in anterior ventral microtubule (AVM) axon regeneration. In older AVM axons, let-7 inhibits regeneration by down-regulating LIN-41, an important AVM axon regeneration-promoting factor. Whereas let-7 inhibits lin-41 expression in older neurons through the lin-41 3' untranslated region, lin-41 inhibits let-7 expression in younger neurons through Argonaute ALG-1. This reciprocal inhibition ensures that axon regeneration is inhibited only in older neurons. These findings show that a let-7-lin-41 regulatory circuit, which was previously …
The Evolution Of Our Thinking About Micrornas, Victor Ambros
The Evolution Of Our Thinking About Micrornas, Victor Ambros
Victor R. Ambros
Our appreciation of the significance of microRNAs to biology at large continues to be an evolving process.
Circulating Micrornas In Cardiovascular Disease, David Mcmanus, Victor Ambros
Circulating Micrornas In Cardiovascular Disease, David Mcmanus, Victor Ambros
Victor R. Ambros
Comment on: Transcoronary concentration gradients of circulating microRNAs. [Circulation. 2011]
Micrornas And Developmental Timing, Victor Ambros
Micrornas And Developmental Timing, Victor Ambros
Victor R. Ambros
MicroRNAs regulate temporal transitions in gene expression associated with cell fate progression and differentiation throughout animal development. Genetic analysis of developmental timing in the nematode Caenorhabditis elegans identified two evolutionarily conserved microRNAs, lin-4/mir-125 and let-7, that regulate cell fate progression and differentiation in C. elegans cell lineages. MicroRNAs perform analogous developmental timing functions in other animals, including mammals. By regulating cell fate choices and transitions between pluripotency and differentiation, microRNAs help to orchestrate developmental events throughout the developing animal, and to play tissue homeostasis roles important for disease, including cancer.
Dauer Larva Quiescence Alters The Circuitry Of Microrna Pathways Regulating Cell Fate Progression In C. Elegans, Xantha Karp, Victor Ambros
Dauer Larva Quiescence Alters The Circuitry Of Microrna Pathways Regulating Cell Fate Progression In C. Elegans, Xantha Karp, Victor Ambros
Victor R. Ambros
In C. elegans larvae, the execution of stage-specific developmental events is controlled by heterochronic genes, which include those encoding a set of transcription factors and the microRNAs that regulate the timing of their expression. Under adverse environmental conditions, developing larvae enter a stress-resistant, quiescent stage called 'dauer'. Dauer larvae are characterized by the arrest of all progenitor cell lineages at a stage equivalent to the end of the second larval stage (L2). If dauer larvae encounter conditions favorable for resumption of reproductive growth, they recover and complete development normally, indicating that post-dauer larvae possess mechanisms to accommodate an indefinite period …
Nhl-2 Modulates Microrna Activity In Caenorhabditis Elegans, Christopher Hammell, Isabella Lubin, Peter Boag, T. Keith Blackwell, Victor Ambros
Nhl-2 Modulates Microrna Activity In Caenorhabditis Elegans, Christopher Hammell, Isabella Lubin, Peter Boag, T. Keith Blackwell, Victor Ambros
Victor R. Ambros
TRIM-NHL proteins represent a large class of metazoan proteins implicated in development and disease. We demonstrate that a C. elegans TRIM-NHL protein, NHL-2, functions as a cofactor for the microRNA-induced silencing complex (miRISC) and thereby enhances the posttranscriptional repression of several genetically verified microRNA targets, including hbl-1 and let-60/Ras (by the let-7 family of microRNAs) and cog-1 (by the lsy-6 microRNA). NHL-2 is localized to cytoplasmic P-bodies and physically associates with the P-body protein CGH-1 and the core miRISC components ALG-1/2 and AIN-1. nhl-2 and cgh-1 mutations compromise the repression of microRNA targets in vivo but do not affect microRNA …
Mirwip: Microrna Target Prediction Based On Microrna-Containing Ribonucleoprotein-Enriched Transcripts, Molly Hammell, Dang Long, Liang Zhang, Andrew Lee, C. Steven Carmack, Min Han, Ye Ding, Victor Ambros
Mirwip: Microrna Target Prediction Based On Microrna-Containing Ribonucleoprotein-Enriched Transcripts, Molly Hammell, Dang Long, Liang Zhang, Andrew Lee, C. Steven Carmack, Min Han, Ye Ding, Victor Ambros
Victor R. Ambros
Target prediction for animal microRNAs (miRNAs) has been hindered by the small number of verified targets available to evaluate the accuracy of predicted miRNA-target interactions. Recently, a dataset of 3,404 miRNA-associated mRNA transcripts was identified by immunoprecipitation of the RNA-induced silencing complex components AIN-1 and AIN-2. Our analysis of this AIN-IP dataset revealed enrichment for defining characteristics of functional miRNA-target interactions, including structural accessibility of target sequences, total free energy of miRNA-target hybridization and topology of base-pairing to the 5' seed region of the miRNA. We used these enriched characteristics as the basis for a quantitative miRNA target prediction method, …
Systematic Analysis Of Dynamic Mirna-Target Interactions During C. Elegans Development, Liang Zhang, Molly Hammell, Brian Kudlow, Victor Ambros, Min Han
Systematic Analysis Of Dynamic Mirna-Target Interactions During C. Elegans Development, Liang Zhang, Molly Hammell, Brian Kudlow, Victor Ambros, Min Han
Victor R. Ambros
Although microRNA (miRNA)-mediated functions have been implicated in many aspects of animal development, the majority of miRNA::mRNA regulatory interactions remain to be characterized experimentally. We used an AIN/GW182 protein immunoprecipitation approach to systematically analyze miRNA::mRNA interactions during C. elegans development. We characterized the composition of miRNAs in functional miRNA-induced silencing complexes (miRISCs) at each developmental stage and identified three sets of miRNAs with distinct stage-specificity of function. We then identified thousands of miRNA targets in each developmental stage, including a significant portion that is subject to differential miRNA regulation during development. By identifying thousands of miRNA family-mRNA pairs with temporally …
Immunopurification Of Ago1 Mirnps Selects For A Distinct Class Of Microrna Targets, Xin Hong, Molly Hammell, Victor Ambros, Stephen Cohen
Immunopurification Of Ago1 Mirnps Selects For A Distinct Class Of Microrna Targets, Xin Hong, Molly Hammell, Victor Ambros, Stephen Cohen
Victor R. Ambros
microRNAs comprise a few percent of animal genes and have been recognized as important regulators of a diverse range of biological processes. Understanding the biological functions of miRNAs requires effective means to identify their targets. Combined efforts from computational prediction, miRNA over-expression or depletion, and biochemical purification have identified thousands of potential miRNA-target pairs in cells and organisms. Complementarity to the miRNA seed sequence appears to be a common principle in target recognition. Other features, including miRNA-target duplex stability, binding site accessibility, and local UTR structure might affect target recognition. Yet computational approaches using such contextual features have yielded largely …
Micrornas: Genetically Sensitized Worms Reveal New Secrets, Victor Ambros
Micrornas: Genetically Sensitized Worms Reveal New Secrets, Victor Ambros
Victor R. Ambros
Why do many microRNA gene mutants display no evident phenotype? Multiply mutant worms that are selectively impaired in genetic regulatory network activities have been used to uncover previously unknown functions for numerous Caenorhabditis elegans microRNAs.
Alcohol And Hcv: Implications For Liver Cancer, Gyongyi Szabo, Banishree Saha, Terence Bukong
Alcohol And Hcv: Implications For Liver Cancer, Gyongyi Szabo, Banishree Saha, Terence Bukong
Gyongyi Szabo
Liver cancers are one of the deadliest known malignancies which are increasingly becoming a major public health problem in both developed and developing countries. Overwhelming evidence suggests a strong role of infection with hepatitis B and C virus (HBV and HCV), alcohol abuse, as well as metabolic diseases such as obesity and diabetes either individually or synergistically to cause or exacerbate the development of liver cancers. Although numerous etiologic mechanisms for liver cancer development have been advanced and well characterized, the lack of definite curative treatments means that gaps in knowledge still exist in identifying key molecular mechanisms and pathways …
Alcohol Facilitates Hcv Rna Replication Via Up-Regulation Of Mir-122 Expression And Inhibition Of Cyclin G1 In Human Hepatoma Cells, Wei Hou, Terence Bukong, Karen Kodys, Gyongyi Szabo
Alcohol Facilitates Hcv Rna Replication Via Up-Regulation Of Mir-122 Expression And Inhibition Of Cyclin G1 In Human Hepatoma Cells, Wei Hou, Terence Bukong, Karen Kodys, Gyongyi Szabo
Gyongyi Szabo
BACKGROUND: Clinical studies demonstrate synergistic liver damage by alcohol and hepatitis C virus (HCV); however, the mechanisms by which alcohol promotes HCV infection remain obscure. The liver-specific microRNA-122 (miR-122) regulates HCV replication and expression of host genes, including Cyclin G1. Here, we hypothesized that alcohol regulates miR-122 expression and thereby modulates HCV RNA replication. METHODS: The J6/JFH/Huh-7.5 model of HCV infection was used in this study. Real-time quantitative polymerase chain reaction, Western blotting, electrophoretic mobility shift assay, and confocal microscopy were used for experimental analysis. RESULTS: We found that acute alcohol exposure (25 mM) significantly increased intracellular HCV RNA as …
Micrornas In Liver Disease, Gyongyi Szabo, Shashi Bala
Micrornas In Liver Disease, Gyongyi Szabo, Shashi Bala
Gyongyi Szabo
Small, noncoding microRNAs (miRNAs) regulate diverse biological functions in the liver and increasing evidence suggests that they have a role in liver pathology. This Review summarizes advances in the field of miRNAs in liver diseases, inflammation and cirrhosis. MicroRNA-122, the most abundant miRNA in hepatocytes, has well-defined roles in HCV replication, and data indicate that it also serves as a viable therapeutic target. The role of miR-122 is also emerging in other liver diseases. Ample evidence exists for the important regulatory potential of other miRNAs in conditions associated with liver inflammation related to alcohol use, the metabolic syndrome or autoimmune …
Advanced Molecular Biologic Techniques In Toxicologic Disease, Jeanine Ward, Gyongyi Szabo, David Mcmanus, Edward Boyer
Advanced Molecular Biologic Techniques In Toxicologic Disease, Jeanine Ward, Gyongyi Szabo, David Mcmanus, Edward Boyer
Gyongyi Szabo
The advancement of molecular biologic techniques and their capabilities to answer questions pertaining to mechanisms of pathophysiologic events have greatly expanded over the past few years. In particular, these opportunities have provided researchers and clinicians alike the framework from with which to answer clinical questions not amenable for elucidation using previous, more antiquated methods. Utilizing extremely small molecules, namely microRNA, DNA, protein, and nanoparticles, we discuss the background and utility of these approaches to the progressive, practicing physician. Finally, we consider the application of these tools employed as future bedside point of care tests, aiding in the ultimate goal of …
Circulating Micrornas In Exosomes Indicate Hepatocyte Injury And Inflammation In Alcoholic, Drug-Induced, And Inflammatory Liver Diseases, Shashi Bala, Jan Petrasek, Shiv Mundkur, Donna Catalano, Ivan Levin, Jeanine Ward, Hawau Alao, Karen Kodys, Gyongyi Szabo
Circulating Micrornas In Exosomes Indicate Hepatocyte Injury And Inflammation In Alcoholic, Drug-Induced, And Inflammatory Liver Diseases, Shashi Bala, Jan Petrasek, Shiv Mundkur, Donna Catalano, Ivan Levin, Jeanine Ward, Hawau Alao, Karen Kodys, Gyongyi Szabo
Gyongyi Szabo
MicroRNAs are fine tuners of diverse biological responses and are expressed in various cell types of the liver. Here we hypothesized that circulating microRNAs (miRNAs) may serve as biomarkers of liver damage and inflammation. We studied miRNA-122, which is abundant in hepatocytes, and miR-155, -146a, and -125b, which regulate inflammation in immune cells in mouse models of alcoholic liver disease (ALD), drug (acetaminophen, APAP)-induced liver injury (DILI), and Toll-like receptor (TLR) 9+4 ligand-induced inflammatory cell-mediated liver damage. We found that serum/plasma miR-122 correlated with alanine aminotransferase (ALT) increases in the liver damage caused by alcohol, APAP, and TLR9 (CpG)+4 (LPS) …
Microrna Expression Profile In Lieber-Decarli Diet-Induced Alcoholic And Methionine Choline Deficient Diet-Induced Nonalcoholic Steatohepatitis Models In Mice, Angela Dolganiuc, Jan Petrasek, Karen Kodys, Donna Catalano, Pranoti Mandrekar, Arumugam Velayudham, Gyongyi Szabo
Microrna Expression Profile In Lieber-Decarli Diet-Induced Alcoholic And Methionine Choline Deficient Diet-Induced Nonalcoholic Steatohepatitis Models In Mice, Angela Dolganiuc, Jan Petrasek, Karen Kodys, Donna Catalano, Pranoti Mandrekar, Arumugam Velayudham, Gyongyi Szabo
Gyongyi Szabo
BACKGROUND: Alcoholic and nonalcoholic steatohepatitis are leading causes of liver diseases worldwide. While of different etiology, these share common pathophysiological mechanisms and feature abnormal fat metabolism, inflammation and fibrosis. MicroRNAs (miRNA) are highly conserved noncoding RNAs that control gene expression at the post-transcriptional level either via the degradation of target mRNAs or the inhibition of translation. Each miRNA controls the expression of multiple targets; miRNAs have been linked to regulation of lipid metabolism and inflammation. METHODS: We fed Lieber-DeCarli alcohol or methionine-choline-deficient (MCD) diets to C57Bl6 and analyzed livers for histopathology, cytokines by ELISA, alanine aminotransferase (ALT) by biochemical assay, …
The Regulation Of Genes And Genomes By Small Rnas., Victor Ambros, Xuemei Chen
The Regulation Of Genes And Genomes By Small Rnas., Victor Ambros, Xuemei Chen
Victor R. Ambros
A recent Keystone Symposium on 'MicroRNAs and siRNAs: Biological Functions and Mechanisms' was organized by David Bartel and Shiv Grewal (and was held in conjunction with 'RNAi for Target Validation and as a Therapeutic', organized by Stephen Friend and John Maraganore). The 'MicroRNAs and siRNAs' meeting brought together scientists working on diverse biological aspects of small regulatory RNAs, including microRNAs, small interfering RNAs (siRNAs) and Piwi-interacting RNAs (piRNAs and rasiRNAs). Among the themes discussed were the diversity of small regulatory RNAs and their developmental functions, their biogenesis, the identification of their regulatory targets, their mechanisms of action, and their roles …
Potent Effect Of Target Structure On Microrna Function, Peter Williams, Dang Long, Rosalind Lee, Chi Chan, Victor Ambros, Ye Ding
Potent Effect Of Target Structure On Microrna Function, Peter Williams, Dang Long, Rosalind Lee, Chi Chan, Victor Ambros, Ye Ding
Victor R. Ambros
MicroRNAs (miRNAs) are small noncoding RNAs that repress protein synthesis by binding to target messenger RNAs. We investigated the effect of target secondary structure on the efficacy of repression by miRNAs. Using structures predicted by the Sfold program, we model the interaction between an miRNA and a target as a two-step hybridization reaction: nucleation at an accessible target site followed by hybrid elongation to disrupt local target secondary structure and form the complete miRNA-target duplex. This model accurately accounts for the sensitivity to repression by let-7 of various mutant forms of the Caenorhabditis elegans lin-41 3' untranslated region and for …
Characterization Of Microrna Expression Levels And Their Biological Correlates In Human Cancer Cell Lines., Caifu Chen, Arti Gaur, David Jewell, Yu Liang, Dana Ridzon, Jason Moore, Victor Ambros, Mark Israel
Characterization Of Microrna Expression Levels And Their Biological Correlates In Human Cancer Cell Lines., Caifu Chen, Arti Gaur, David Jewell, Yu Liang, Dana Ridzon, Jason Moore, Victor Ambros, Mark Israel
Victor R. Ambros
MicroRNAs are small noncoding RNAs that function by regulating target gene expression posttranscriptionally. They play a critical role in developmental and physiologic processes and are implicated in the pathogenesis of several human diseases including cancer. We examined the expression profiles of 241 human microRNAs in normal tissues and the NCI-60 panel of human tumor-derived cell lines. To quantify microRNA expression, we employed a highly sensitive technique that uses stem-loop primers for reverse transcription followed by real-time PCR. Most microRNAs were expressed at lower levels in tumor-derived cell lines compared with the corresponding normal tissue. Agglomerative hierarchical clustering analysis of microRNA …
Developmental Biology. Encountering Micrornas In Cell Fate Signaling., Xantha Karp, Victor Ambros
Developmental Biology. Encountering Micrornas In Cell Fate Signaling., Xantha Karp, Victor Ambros
Victor R. Ambros
Comment on: LIN-12/Notch activation leads to microRNA-mediated down-regulation of Vav in C. elegans. [Science. 2005]
The Functions Of Animal Micrornas., Victor Ambros
The Functions Of Animal Micrornas., Victor Ambros
Victor R. Ambros
MicroRNAs (miRNAs) are small RNAs that regulate the expression of complementary messenger RNAs. Hundreds of miRNA genes have been found in diverse animals, and many of these are phylogenetically conserved. With miRNA roles identified in developmental timing, cell death, cell proliferation, haematopoiesis and patterning of the nervous system, evidence is mounting that animal miRNAs are more numerous, and their regulatory impact more pervasive, than was previously suspected.
A Short History Of A Short Rna, Victor Ambros, Rosalind Lee, Rhonda Feinbaum
A Short History Of A Short Rna, Victor Ambros, Rosalind Lee, Rhonda Feinbaum
Victor R. Ambros
Comment on: The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14. [Cell. 1993]
Identification Of Micrornas And Other Tiny Noncoding Rnas By Cdna Cloning, Victor Ambros, Rosalind Lee
Identification Of Micrornas And Other Tiny Noncoding Rnas By Cdna Cloning, Victor Ambros, Rosalind Lee
Victor R. Ambros
MicroRNAs (miRNAs) and other small RNAs can be identified by cloning and sequencing cDNAs prepared from the ∼22-nt fraction of total RNA. Methods are described for the construction of cDNA libraries from small noncoding RNAs through the use of T4 RNA ligase, reverse transcriptase, and polymerase chain reaction. cDNAs are cloned in λ or plasmid vectors, and the sequences are compared to annotated genomic sequence databases, and analyzed by RNA folding programs to distinguish miRNA sequences from other small RNAs of similar size. Northern blot hybridization is used to confirm the expression of small RNAs in vivo.
Role Of Micrornas In Plant And Animal Development, Victor Ambros, James Carrington
Role Of Micrornas In Plant And Animal Development, Victor Ambros, James Carrington
Victor R. Ambros
Small RNAs, including microRNAs (miRNAs) and short interfering RNAs (siRNAs), are key components of an evolutionarily conserved system of RNA-based gene regulation in eukaryotes. They are involved in many molecular interactions, including defense against viruses and regulation of gene expression during development. miRNAs interfere with expression of messenger RNAs encoding factors that control developmental timing, stem cell maintenance, and other developmental and physiological processes in plants and animals. miRNAs are negative regulators that function as specificity determinants, or guides, within complexes that inhibit protein synthesis (animals) or promote degradation (plants) of mRNA targets.
Microrna Pathways In Flies And Worms: Growth, Death, Fat, Stress, And Timing, Victor Ambros
Microrna Pathways In Flies And Worms: Growth, Death, Fat, Stress, And Timing, Victor Ambros
Victor R. Ambros
Drosophila geneticists have uncovered roles for microRNAs in the coordination of cell proliferation and cell death during development, and in stress resistance and fat metabolism. In C. elegans, a homolog of the well-known fly developmental regulator hunchback acts downstream of the microRNAs lin-4 and let-7 in a pathway controlling developmental timing.
Micrornas And Other Tiny Endogenous Rnas In C. Elegans, Victor Ambros, Rosalind Lee, Ann Lavanway, Peter Williams, David Jewell
Micrornas And Other Tiny Endogenous Rnas In C. Elegans, Victor Ambros, Rosalind Lee, Ann Lavanway, Peter Williams, David Jewell
Victor R. Ambros
BACKGROUND: MicroRNAs (miRNAs) are small noncoding RNAs that are processed from hairpin precursor transcripts by Dicer. miRNAs probably inhibit translation of mRNAs via imprecise antisense base-pairing. Small interfering RNAs (siRNAs) are similar in size to miRNAs, but they recognize targets by precise complementarity and elicit RNA-mediated interference (RNAi). We employed cDNA sequencing and comparative genomics to identify additional C. elegans small RNAs with properties similar to miRNAs and siRNAs. RESULTS: We found three broad classes of small RNAs in C. elegans: (1) 21 new miRNA genes (we estimate that C. elegans contains approximately 100 distinct miRNA genes, about 30% of …
Micrornas: Tiny Regulators With Great Potential, Victor Ambros
Micrornas: Tiny Regulators With Great Potential, Victor Ambros
Victor R. Ambros
Animal genomes contain an abundance of small genes that produce regulatory RNAs of about 22 nucleotides in length. These microRNAs are diverse in sequence and expression patterns, and are evolutionarily widespread, suggesting that they may participate in a wide range of genetic regulatory pathways.