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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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Oct 2015

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 Jun 2015

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 …