Biochemistry, Biophysics, and Structural Biology Commons^™

Genetic And Acute Cpeb1 Depletion Ameliorate Fragile X Pathophysiology, Tsuyoshi Udagawa, Natalie Farny, Mira Jakovcevski, Hanoch Kaphzan, Juan Alarcon, Shobha Anilkumar, Maria Ivshina, Jessica Hurt, Kentaro Nagaoka, Vijayalaxmi Nalavadi, Lori Lorenz, Gary Bassell, Schahram Akbarian, Sumantra Chattarji, Eric Klann, Joel Richter

Natalie G. Farny

Fragile X syndrome (FXS), the most common cause of inherited mental retardation and autism, is caused by transcriptional silencing of FMR1, which encodes the translational repressor fragile X mental retardation protein (FMRP). FMRP and cytoplasmic polyadenylation element-binding protein (CPEB), an activator of translation, are present in neuronal dendrites, are predicted to bind many of the same mRNAs and may mediate a translational homeostasis that, when imbalanced, results in FXS. Consistent with this possibility, Fmr1(-/y); Cpeb1(-/-) double-knockout mice displayed amelioration of biochemical, morphological, electrophysiological and behavioral phenotypes associated with FXS. Acute depletion of CPEB1 in the hippocampus of adult Fmr1(-/y) mice …

Characterization And Structure Of A Zn2+ And [2fe-2s]-Containing Copper Chaperone From Archaeoglobus Fulgidus, Matthew Sazinsky, Benjamin Lemoine, Maria Orofino, Roman Davydov, Krisztina Bencze, Timothy Stemmler, Brian Hoffman, José Argüello, Amy Rosenzweig

José M. Argüello

Bacterial CopZ proteins deliver copper to P1B-type Cu+-ATPases that are homologous to the human Wilson and Menkes disease proteins. The genome of the hyperthermophile Archaeoglobus fulgidus encodes a putative CopZ copper chaperone that contains an unusual cysteine rich N-terminal domain of 130 amino acids in addition to a C-terminal copper-binding domain with a conserved CXXC motif. The N-terminal domain (CopZ-NT) is homologous to proteins found only in extremophiles and is the only such protein that is fused to a copper chaperone. Surprisingly, optical, electron paramagnetic resonance, and X-ray absorption spectroscopic data indicate the presence of a [2Fe-2S] cluster in CopZ-NT. …

Correlations Between Oxygen Affinity And Sequence Classifications Of Plant Hemoglobins, Benoit Smagghe, Julie Hoy, Ryan Percifield, Suman Kundu, Mark Hargrove, Gautam Sarath, Jean-Louis Hilbert, Richard Watts, Elizabeth Dennis, W. James Peacock, Sylvia Dewilde, Luc Moens, George Blouin, John Olson, Cyril Appleby

John Olson

Plants express three phylogenetic classes of hemoglobins (Hb) based on sequence analyses. Class 1 and 2 Hbs are full-length globins with the classical eight helix Mb-like fold, whereas Class 3 plant Hbs resemble the truncated globins found in bacteria. With the exception of the specialized leghemoglobins, the physiological functions of these plant hemoglobins remain unknown. We have reviewed and, in some cases, measured new oxygen binding properties of a large number of Class 1 and 2 plant nonsymbiotic Hbs and leghemoglobins. We found that sequence classification correlates with distinct extents of hexacoordination with the distal histidine and markedly different overall …

A 4d View On Mrna, Carlas Smith, Li-Chun Tu, David Grünwald

David Grünwald

Imaging single molecules in live cells in 4+ D (space, time and colors) is crucial for studying various biological processes, especially for observing the behavior of RNA molecules within the nuclear landscape [1]. RNA molecules are known to serve a multitude of tasks such as being templates for protein translation or to act as enzymes for regulating countless reactions in the nucleus [1]. Studying RNA kinetics in living cells can provide new information on RNA function or even human diseases, for instance caused by viruses such as the human immunodeficiency virus (HIV) [2]. A challenge to imaging nuclear RNA function …

Transforming Growth Factor Betas Induce Mmp-2 And Mmp-9 Secretion Via Smad-Dependent Signaling In Human Endometrial And Endometriotic Cells, Ezekiel O. Mecha, Cong Sui, Charles O.A . Omwandho, Hans-Rudolf Tinneberg, Lutz Konrad

Innovative Research Publications IRP India

Transforming growth factor-betas (TGF-βs) are elevated during menstruation and are involved in endometriosis. Similarly, matrix metalloproteinases like MMP-2 are also highly expressed in patients with endometriosis. Expression of gelatinases, MMP-2 and MMP-9, is increased by TGF-βs. TGF- βs bind and activate receptor-mediated Smad proteins to mediate gene expression, however, also non-Smad signaling pathways participate in signal transduction of the TGF-βs. In this study, we found that of MMP-2 and MMP-9 is higher in stromal cells especially in endometriotic cells compared to epithelial cells. Treatment of endometrial and endometriotic stromal and epithelial cells with TGF-β1 or TGF-β2 decreased cell numbers, induced …

Cytoplasmic Ph Measurement And Homeostasis In Bacteria And Archaea., Joan Slonczewski

Joan Slonczewski

Of all the molecular determinants for growth, the hydronium and hydroxide ions are found naturally in the widest concentration range, from acid mine drainage below pH 0 to soda lakes above pH 13. Most bacteria and archaea have mechanisms that maintain their internal, cytoplasmic pH within a narrower range than the pH outside the cell, termed "pH homeostasis." Some mechanisms of pH homeostasis are specific to particular species or groups of microorganisms while some common principles apply across the pH spectrum. The measurement of internal pH of microbes presents challenges, which are addressed by a range of techniques under varying …

Ph Of The Cytoplasm And Periplasm Of Escherichia Coli: Rapid Measurement By Green Fluorescent Protein Fluorimetry, Joan Slonczewski, Jessica C. Wilks

Joan Slonczewski

Cytoplasmic pH and periplasmic pH of Escherichia coli cells in suspension were observed with 4-s time resolution using fluorimetry of TorA-green fluorescent protein mutant 3* (TorA-GFPmut3*) and TetR-yellow fluorescent protein. Fluorescence intensity was correlated with pH using cell suspensions containing 20 mM benzoate, which equalizes the cytoplasmic pH with the external pH. When the external pH was lowered from pH 7.5 to 5.5, the cytoplasmic pH fell within 10 to 20 s to pH 5.6 to 6.5. Rapid recovery occurred until about 30 s after HCl addition and was followed by slower recovery over the next 5 min. As a …

Cytoplasmic Ph Response To Acid Stress In Individual Cells Of Escherichia Coli And Bacillus Subtilis Observed By Fluorescence Ratio Imaging Microscopy, Joan Slonczewski, Keith A. Martinez Ii, Ryan D. Kitko, J. Patrick Mershon, Haley E. Adcox, Kotiba A. Malek, Melanie B. Berkmen

Joan Slonczewski

The ability of Escherichia coli and Bacillus subtilis to regulate their cytoplasmic pH is well studied in cell suspensions but is poorly understood in individual adherent cells and biofilms. We observed the cytoplasmic pH of individual cells using ratiometric pHluorin. A standard curve equating the fluorescence ratio with pH was obtained by perfusion at a range of external pH 5.0 to 9.0, with uncouplers that collapse the transmembrane pH difference. Adherent cells were acid stressed by switching the perfusion medium from pH 7.5 to pH 5.5. The E. coli cytoplasmic pH fell to a value that varied among individual cells …

Ph Regulates Genes For Flagellar Motility, Catabolism, And Oxidative Stress In Escherichia Coli K-12†, Joan Slonczewski

Joan Slonczewski

Gene expression profiles of Escherichia coli K-12 W3110 were compared as a function of steady-state external pH. Cultures were grown to an optical density at 600 nm of 0.3 in potassium-modified Luria-Bertani medium buffered at pH 5.0, 7.0, and 8.7. For each of the three pH conditions, cDNA from RNA of five independent cultures was hybridized to Affymetrix E. coli arrays. Normalized expression indices were calculated for each gene and intergenic region (IG). Differential expression among the three pH classes was observed for 763 genes and 353 IGs. Hierarchical clustering yielded six well-defined clusters of pH profiles, designated Acid High …

Generalization Of Dna Microarray Dispersion Properties: Microarray Equivalent Of T-Distribution, Joan Slonczewski

Joan Slonczewski

Background: DNA microarrays are a powerful technology that can provide a wealth of gene expression data for disease studies, drug development, and a wide scope of other investigations. Because of the large volume and inherent variability of DNA microarray data, many new statistical methods have been developed for evaluating the significance of the observed differences in gene expression. However, until now little attention has been given to the characterization of dispersion of DNA microarray data. Results: Here we examine the expression data obtained from 682 Affymetrix GeneChips® with 22 different types and we demonstrate that the Gaussian (normal) frequency distribution …

Escherichia Coli K-12 Survives Anaerobic Exposure At Ph 2 Without Rpos, Gad, Or Hydrogenases, But Shows Sensitivity To Autoclaved Broth Products, Joan Slonczewski, Daniel P. Riggins, Maria J. Narvaez, Keith A. Martinez, Mark M. Harden

Joan Slonczewski

Escherichia coli and other enteric bacteria survive exposure to extreme acid (pH 2 or lower) in gastric fluid. Aerated cultures survive via regulons expressing glutamate decarboxylase (Gad, activated by RpoS), cyclopropane fatty acid synthase (Cfa) and others. But extreme-acid survival is rarely tested under low oxygen, a condition found in the stomach and the intestinal tract. We observed survival of E. coli K-12 W3110 at pH 1.2–pH 2.0, conducting all manipulations (overnight culture at pH 5.5, extreme-acid exposure, dilution and plating) in a glove box excluding oxygen (10% H2, 5% CO2, balance N2). With dissolved O2 concentrations maintained below 6 …

Hydrogenase-3 Contributes To Anaerobic Acid Resistance Of Escherichia Coli, Joan Slonczewski, Ken Noguchi, Daniel P. Riggins, Khalid C. Eldahan, Ryan D. Kitko

Joan Slonczewski

Background: Hydrogen production by fermenting bacteria such as Escherichia coli offers a potential source of hydrogen biofuel. Because H2 production involves consumption of 2H+ , hydrogenase expression is likely to involve pH response and regulation. Hydrogenase consumption of protons in E. coli has been implicated in acid resistance, the ability to survive exposure to acid levels (pH 2–2.5) that are three pH units lower than the pH limit of growth (pH 5–6). Enhanced survival in acid enables a larger infective inoculum to pass through the stomach and colonize the intestine. Most acid resistance mechanisms have been defined using aerobic cultures, …

Osmolytes Contribute To Ph Homeostasis Of Escherichia Coli, Joan Slonczewski, Ryan D. Kitko, Jessica C. Wilks, Gian M. Garduque

Joan Slonczewski

Background: Cytoplasmic pH homeostasis in Escherichia coli includes numerous mechanisms involving pH-dependent catabolism and ion fluxes. An important contributor is transmembrane K+ flux, but the actual basis of K+ compensation for pH stress remains unclear. Osmoprotection could mediate the pH protection afforded by K+ and other osmolytes. Methods and Principal Findings: The cytoplasmic pH of E. coli K-12 strains was measured by GFPmut3 fluorimetry. The wild-type strain Frag1 was exposed to rapid external acidification by HCl addition. Recovery of cytoplasmic pH was enhanced equally by supplementation with NaCl, KCl, proline, or sucrose. A triple mutant strain TK2420 defective for the …

Oxygen Limitation Modulates Ph Regulation Of Catabolism And Hydrogenases, Multidrug Transporters, And Envelope Composition In Escherichia Coli K-12, Joan Slonczewski, Everett T. Hayes, Jessica C. Wilks, Piero Sanfilippo, Elizabeth Yohannes, Daniel P. Tate, Brian D. Jones, Michael D. Radmacher, Sandra S. Bondurant

Joan Slonczewski

Background: In Escherichia coli, pH regulates genes for amino-acid and sugar catabolism, electron transport, oxidative stress, periplasmic and envelope proteins. Many pH-dependent genes are co-regulated by anaerobiosis, but the overall intersection of pH stress and oxygen limitation has not been investigated. Results: The pH dependence of gene expression was analyzed in oxygen-limited cultures of E. coli K-12 strain W3110. E. coli K-12 strain W3110 was cultured in closed tubes containing LBK broth buffered at pH 5.7, pH 7.0, and pH 8.5. Affymetrix array hybridization revealed pH-dependent expression of 1,384 genes and 610 intergenic regions. A core group of 251 genes …

Ph-Dependent Expression Of Periplasmic Proteins And Amino Acid Catabolism In Escherichia Coli, Joan Slonczewski, Lauren M. Stancik, Dawn M. Stancik, Brian Schmidt, D. Michael Barnhart, Yuliya N. Yoncheva

Joan Slonczewski

Escherichia coli grows over a wide range of pHs (pH 4.4 to 9.2), and its own metabolism shifts the external pH toward either extreme, depending on available nutrients and electron acceptors. Responses to pH values across the growth range were examined through two-dimensional electrophoresis (2-D gels) of the proteome and through lac gene fusions. Strain W3110 was grown to early log phase in complex broth buffered at pH 4.9, 6.0, 8.0, or 9.1. 2-D gel analysis revealed the pH dependence of 19 proteins not previously known to be pH dependent. At low pH, several acetate-induced proteins were elevated (LuxS, Tpx, …

Ph-Dependent Catabolic Protein Expression During Anaerobic Growth Of Escherichia Coli K-12, Joan Slonczewski, Elizabeth Yohannes, D. Michael Barnhart

Joan Slonczewski

During aerobic growth of Escherichia coli, expression of catabolic enzymes and envelope and periplasmic proteins is regulated by pH. Additional modes of pH regulation were revealed under anaerobiosis. E. coli K-12 strain W3110 was cultured anaerobically in broth medium buffered at pH 5.5 or 8.5 for protein identification on proteomic two-dimensional gels. A total of 32 proteins from anaerobic cultures show pH-dependent expression, and only four of these proteins (DsbA, TnaA, GatY, and HdeA) showed pH regulation in aerated cultures. The levels of 19 proteins were elevated at the high pH; these proteins included metabolic enzymes (DhaKLM, GapA, TnaA, HisC, …

Polyamine Stress At High Ph In Escherichia Coli K-12, Joan Slonczewski, Elizabeth Yohannes, Amy E. Thurber, Jessica C. Wilks, Daniel P. Tate

Joan Slonczewski

Background: Polyamines such as spermine and spermidine are required for growth of Escherichia coli; they interact with nucleic acids, and they bind to ribosomes. Polyamines block porins and decrease membrane permeability, activities that may protect cells in acid. At high concentrations, however, polyamines impair growth. They impair growth more severely at high pH, probably due to their increased uptake as membrane-permeant weak bases. The role of pH is critical in understanding polyamine stress. Results: The effect of polyamines was tested on survival of Escherichia coli K-12 W3110 in extreme acid or base (pH conditions outside the growth range). At pH …

Mcnamara 201412 Nih Scap Innocentive Challenge Solution - T-Bow Rainbow T-Cells And Tumor Cells Spatial Multiplexing Gene Expression Reporter System – Plus Supplement Plus Posters - 20151027 - Please Download "75" Instead, George Mcnamara

George McNamara

McNamara 201412 NIH SCAP InnoCentive Challenge Solution - T-Bow Rainbow T-cells and Tumor Cells Spatial Multiplexing Gene Expression Reporter System – plus supplement plus posters - 20151027.

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Please download the current 20151027 (October 27, 2015) Tattletales and T-Bow update from

http://works.bepress.com/gmcnamara/75/

The bepress web site is not letting me replace the old pdf here at "65" with the additional 10 pages update.

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The download is my/Cooper lab solution (submission) to the 2014 NIH Single Cell Analysis Program (SCAP) InnoCentive Challenge, "Follow That Cell". I submitted the Solution on 20141215Mon (with 20 minutes to spare). The Challenge web page …

Tattletales And T-Bow Update 20151027tue, George Mcnamara

George McNamara

20151027Tue this "75"

http://works.bepress.com/gmcnamara/75

is my update of "65" posting

See text at

http://works.bepress.com/gmcnamara/65/

for text summary. The PDf here in "75" supersedes "65".

The PDF here has 10 pages added to the end from the "65" version (pages 40-49 of PDF when including the bepress cover page)..

here is the text in my cover page (bepress may add its own cover):

20151027Tue: added 10 page e-poster at bottom explaining Binary Tattletales and T-Bow. That is, binary with respect to protein components. For one color (number of repeats, epitope tags, FPs are examples, here rounded to convenient numbers):

1. 100 …

Rna Recognition By The Caenorhabditis Elegans Oocyte Maturation Determinant Oma-1, Ebru Kaymak, Sean Ryder

Sean P. Ryder

Maternally supplied mRNAs encode proteins that pattern early embryos in many species. In the nematode Caenorhabditis elegans, a suite of RNA-binding proteins regulates expression of maternal mRNAs during oogenesis, the oocyte to embryo transition, and early embryogenesis. To understand how these RNA-binding proteins contribute to development, it is necessary to determine how they select specific mRNA targets for regulation. OMA-1 and OMA-2 are redundant proteins required for oocyte maturation--an essential part of meiosis that prepares oocytes for fertilization. Both proteins have CCCH type tandem zinc finger RNA-binding domains. Here, we define the RNA binding specificity of OMA-1 and demonstrate that …

Feasibility Study Of Inversely-Optimized Intensity Modulated Grid-Therapy For Bulky Lung Tumors, M Macfarlane, J Lam, R Dar, E Yu, K Jordan, Jz Chen

Edward Yu

Purpose/Objective(s): Grid therapy with megavoltage photon beams has been clinically shown to improve local control of bulky tumors. The purpose of this study is to develop intensity modulated grid therapy (IMGT) with multiple beams. We hypothesize that when compared to conventional single-field grid therapy, IMGT will provide lower spatially fractionated doses to the surrounding organs at risk (OAR) while increasing the minimum dose to the whole tumor volume and thus improve tumor control probability as supported by conventionalradiobiology. Materials/Methods: IMGT was developed with multiple photon beams using dynamic MLC segments and orthogonal blocks. Spatially fractionated fluence patterns for all beams …

Isotopic Discrimination In The Double-Crested Cormorant (Phalacrocorax Auritus), Elizabeth C. Craig, Brian S. Dorr, Katie C. Hanson-Dorr, Jed P. Sparks, Paul D. Curtis

Brian S Dorr

The diet-tissue discrimination factor is the amount by which a consumer’s tissue varies isotopically from its diet, and is therefore a key element in models that use stable isotopes to estimate diet composition. In this study we measured discrimination factors in blood (whole blood, red blood cells and plasma), liver, muscle and feathers of Double- crested Cormorants (Phalacrocorax auritus) for stable isotope ratios of carbon, nitrogen and sulfur. Cormorants exhibited discrimination factors that differed significantly among tissue types (for carbon and nitrogen), and differed substantially (in the context of the isotopic variation among relevant prey species) from those observed in …

Evaluation Of Effective Operational Cycle Time And Bioprocess Parameters In A Sequential Batch Reactor For Efficient Organic And Nutrient Removal From Domestic Sewage, Sandip S. Magdum, Siva Kumar Varigala, Yogesh N. Patil, Gauri P. Minde, Janardhan B. Bornare, V. Kalyanraman

Sandip S. Magdum

Anaerobic, anoxic and aerobic environment can be simulated in the single stage sequential batch reactor (SBR) . Various design conditions viz., combinations of different phase time and different cycle time, hydraulic residence time (HRT), substrate loading rate, sludge age (SRT) and aeration time were analyzed for optimum biological treatment. The pilot runs were evaluated with the design conditions of food/microbe ratio (F/M) 0.2 per day and MLSS of 4950 mg/L. For the given design conditions 4, 5 and 6 hours cycle lengths were analyzed for their efficient performance with 30-33% of decant volume for sewage containing C:N:P of 100:8:2. Studies …

Biodistribution And Function Of Extracellular Mirna-155 In Mice, Shashi Bala, Timea Csak, Fatemeh Momen-Heravi, Dora Lippai, Karen Kodys, Donna Catalano, Abhishek Satishchandran, Victor R. Ambros, Gyongyi Szabo

Gyongyi Szabo

Circulating miRNAs can be found in extracellular vesicles (EV) and could be involved in intercellular communication. Here, we report the biodistribution of EV associated miR-155 using miR-155 KO mouse model. Administration of exosomes loaded with synthetic miR-155 mimic into miR-155 KO mice resulted in a rapid accumulation and clearance of miR-155 in the plasma with subsequent distribution in the liver, adipose tissue, lung, muscle and kidney (highest to lowest, respectively). miR-155 expression was detected in isolated hepatocytes and liver mononuclear cells of recipient KO mice suggesting its cellular uptake. In vitro, exosome-mediated restoration of miR-155 in Kupffer cells from miR-155 …

Caenorhabditis Elegans Alg-1 Antimorphic Mutations Uncover Functions For Argonaute In Microrna Guide Strand Selection And Passenger Strand Disposal, Anna Y. Zinovyeva, Isana Veksler-Lublinsky, Ajay A. Vashisht, James A. Wohlschlegel, Victor R. Ambros

Victor R. Ambros

MicroRNAs are regulators of gene expression whose functions are critical for normal development and physiology. We have previously characterized mutations in a Caenorhabditis elegans microRNA-specific Argonaute ALG-1 (Argonaute-like gene) that are antimorphic [alg-1(anti)]. alg-1(anti) mutants have dramatically stronger microRNA-related phenotypes than animals with a complete loss of ALG-1. ALG-1(anti) miRISC (microRNA induced silencing complex) fails to undergo a functional transition from microRNA processing to target repression. To better understand this transition, we characterized the small RNA and protein populations associated with ALG-1(anti) complexes in vivo. We extensively characterized proteins associated with wild-type and mutant ALG-1 and found that the mutant …

Biodistribution And Function Of Extracellular Mirna-155 In Mice, Shashi Bala, Timea Csak, Fatemeh Momen-Heravi, Dora Lippai, Karen Kodys, Donna Catalano, Abhishek Satishchandran, Victor R. Ambros, Gyongyi Szabo

Victor R. Ambros

Circulating miRNAs can be found in extracellular vesicles (EV) and could be involved in intercellular communication. Here, we report the biodistribution of EV associated miR-155 using miR-155 KO mouse model. Administration of exosomes loaded with synthetic miR-155 mimic into miR-155 KO mice resulted in a rapid accumulation and clearance of miR-155 in the plasma with subsequent distribution in the liver, adipose tissue, lung, muscle and kidney (highest to lowest, respectively). miR-155 expression was detected in isolated hepatocytes and liver mononuclear cells of recipient KO mice suggesting its cellular uptake. In vitro, exosome-mediated restoration of miR-155 in Kupffer cells from miR-155 …

Inhibiting Mirna In Caenorhabditis Elegans Using A Potent And Selective Antisense Reagent, Genhua Zheng, Victor R. Ambros, Wen-Hong Li

Victor R. Ambros

BACKGROUND: Antisense reagents can serve as efficient and versatile tools for studying gene function by inhibiting nucleic acids in vivo. Antisense reagents have particular utility for the experimental manipulation of the activity of microRNAs (miRNAs), which are involved in the regulation of diverse developmental and physiological pathways in animals. Even in traditional genetic systems, such as the nematode Caenorhabditis elegans, antisense reagents can provide experimental strategies complementary to mutational approaches. Presently no antisense reagents are available for inhibiting miRNAs in the nematode C. elegans. RESULTS: We have developed a new class of fluorescently labelled antisense reagents to inhibit miRNAs in …

Control Of Stem Cell Self-Renewal And Differentiation By The Heterochronic Genes And The Cellular Asymmetry Machinery In Caenorhabditis Elegans, Omid F. Harandi, Victor Ambros

Victor R. Ambros

Transitions between asymmetric (self-renewing) and symmetric (proliferative) cell divisions are robustly regulated in the context of normal development and tissue homeostasis. To genetically assess the regulation of these transitions, we used the postembryonic epithelial stem (seam) cell lineages of Caenorhabditis elegans. In these lineages, the timing of these transitions is regulated by the evolutionarily conserved heterochronic pathway, whereas cell division asymmetry is conferred by a pathway consisting of Wnt (Wingless) pathway components, including posterior pharynx defect (POP-1)/TCF, APC related/adenomatosis polyposis coli (APR-1)/APC, and LIT-1/NLK (loss of intestine/Nemo-like kinase). Here we explore the genetic regulatory mechanisms underlying stage-specific transitions between self-renewing …

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

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 …