The Circadian Deadenylase Nocturnin Is Necessary for Stabilization of the iNOS mRNA in Mice

Nocturnin is a member of the CCR4 deadenylase family, and its expression is under circadian control with peak levels at night. Because it can remove poly(A) tails from mRNAs, it is presumed to play a role in post-transcriptional control of circadian gene expression, but its target mRNAs are not known. Here we demonstrate that Nocturnin expression is acutely induced by the endotoxin lipopolysaccharide (LPS). Mouse embryo fibroblasts (MEFs) lacking Nocturnin exhibit normal patterns of acute induction of TNFα and iNOS mRNAs during the first three hours following LPS treatment, but by 24 hours, while TNFα mRNA levels are indistinguishable from WT cells, iNOS message is significantly reduced 20-fold. Accordingly, analysis of the stability of the mRNAs showed that loss of Nocturnin causes a significant decrease in the half-life of the iNOS mRNA (t1/2 = 3.3 hours in Nocturnin knockout MEFs vs. 12.4 hours in wild type MEFs), while having no effect on the TNFα message. Furthermore, mice lacking Nocturnin lose the normal nighttime peak of hepatic iNOS mRNA, and have improved survival following LPS injection. These data suggest that Nocturnin has a novel stabilizing activity that plays an important role in the circadian response to inflammatory signals

MicroRNA-122 Modulates the Rhythmic Expression Profile of the Circadian Deadenylase Nocturnin in Mouse Liver

Nocturnin is a circadian clock-regulated deadenylase thought to control mRNA expression post-transcriptionally through poly(A) tail removal. The expression of Nocturnin is robustly rhythmic in liver at both the mRNA and protein levels, and mice lacking Nocturnin are resistant to diet-induced obesity and hepatic steatosis. Here we report that Nocturnin expression is regulated by microRNA-122 (miR-122), a liver specific miRNA. We found that the 3′-untranslated region (3′-UTR) of Nocturnin mRNA harbors one putative recognition site for miR-122, and this site is conserved among mammals. Using a luciferase reporter construct with wild-type or mutant Nocturnin 3′-UTR sequence, we demonstrated that overexpression of miR-122 can down-regulate luciferase activity levels and that this effect is dependent on the presence of the putative miR-122 recognition site. Additionally, the use of an antisense oligonucleotide to knock down miR-122 in vivo resulted in significant up-regulation of both Nocturnin mRNA and protein expression in mouse liver during the night, resulting in Nocturnin rhythms with increased amplitude. Together, these data demonstrate that the normal rhythmic profile of Nocturnin expression in liver is shaped in part by miR-122. Previous studies have implicated Nocturnin and miR-122 as important post-transcriptional regulators of both lipid metabolism and circadian clock controlled gene expression in the liver. Therefore, the demonstration that miR-122 plays a role in regulating Nocturnin expression suggests that this may be an important intersection between hepatic metabolic and circadian control

Nocturnin Expression Is Induced by Fasting in the White Adipose Tissue of Restricted Fed Mice

The relationship between circadian clocks and metabolism is intimate and complex and a number of recent studies have begun to reveal previously unknown effects of food and its temporal availability on the clock and the rhythmic transcriptome of peripheral tissues. Nocturnin, a circadian deadenylase, is expressed rhythmically in a wide variety of tissues, but we report here that Nocturnin expression is arrhythmic in epididymal white adipose tissue (eWAT) of mice housed in 12∶12 LD with ad libitum access to food. However, Nocturnin expression becomes rhythmic in eWAT of mice placed on restricted feeding. We show here that Nocturnin's rhythmic expression pattern is not dependent upon feeding, nor is it acutely induced by feeding in the liver or eWAT of ad libitum fed mice. However, Nocturnin is acutely induced by the absence of the expected meal in eWAT of restricted fed mice. A rise in cAMP levels also induces Nocturnin expression, suggesting that Nocturnin's induction in eWAT by fasting is likely mediated through the same pathways that activate lipolysis. Therefore, this suggests that Nocturnin plays a role in linking nutrient sensing by the circadian clock to lipid mobilization in the adipocytes

Remote control of gene function by local translation

The subcellular position of a protein is a key determinant of its function. Mounting evidence indicates that RNA localization, where specific mRNAs are transported subcellularly and subsequently translated in response to localized signals, is an evolutionarily conserved mechanism to control protein localization. On-site synthesis confers novel signaling properties to a protein and helps to maintain local proteome homeostasis. Local translation plays particularly important roles in distal neuronal compartments, and dysregulated RNA localization and translation cause defects in neuronal wiring and survival. Here, we discuss key findings in this area and possible implications of this adaptable and swift mechanism for spatial control of gene function

La renovación de la palabra en el bicentenario de la Argentina : los colores de la mirada lingüística

El libro reúne trabajos en los que se exponen resultados de investigaciones presentadas por investigadores de Argentina, Chile, Brasil, España, Italia y Alemania en el XII Congreso de la Sociedad Argentina de Lingüística (SAL), Bicentenario: la renovación de la palabra, realizado en Mendoza, Argentina, entre el 6 y el 9 de abril de 2010. Las temáticas abordadas en los 167 capítulos muestran las grandes líneas de investigación que se desarrollan fundamentalmente en nuestro país, pero también en los otros países mencionados arriba, y señalan además las áreas que recién se inician, con poca tradición en nuestro país y que deberían fomentarse. Los trabajos aquí publicados se enmarcan dentro de las siguientes disciplinas y/o campos de investigación: Fonología, Sintaxis, Semántica y Pragmática, Lingüística Cognitiva, Análisis del Discurso, Psicolingüística, Adquisición de la Lengua, Sociolingüística y Dialectología, Didáctica de la lengua, Lingüística Aplicada, Lingüística Computacional, Historia de la Lengua y la Lingüística, Lenguas Aborígenes, Filosofía del Lenguaje, Lexicología y Terminología

Circadian oscillations and delays in WT and <i>tyf</i> mutant flies.

<p>(A) Time evolution of the <i>per</i> transcript (<i>solid lines</i>) and total PER protein (<i>dashed lines</i>) in WT (<i>black</i>), <i>tyf</i>^<i>Δ</i> (<i>dark gray</i>) and <i>tyf^e</i> (<i>light gray</i>) flies. (B) Delay values (<i>δ_t</i>) of each fly strain. Results obtained with our model for <i>k_s</i> = 0 <i>h</i>^−<i>1</i>, <i>K_r</i> = 0.3 <i>nM h</i>^−<i>1</i> and <i>nH</i> = 4. Dotted line was plotted only for clarity purposes. See the text for further details.</p

Comparison between theoretical and experimental results.

<p>The dashed gray line shows the dependence of <i>τ</i> with the <i>V_r</i> parameter obtained with our model, for <i>k_s</i> = 0 <i>h</i>^−<i>1</i>, <i>K_r</i> = 0.3 <i>nM h</i>^−<i>1</i> and <i>nH</i> = <i>4</i>. The periods of behavioral rhythms in wild type (WT) flies and <i>tyf</i> mutants (<i>tyf^e</i> and <i>tyf</i>^Δ) are also indicated with black points and arrows, according to [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.ref025" target="_blank">25</a>]. See the text for further details</p

Scheme of the ‘master’ model proposed in the present work.

<p>The model is based on a Goodwin oscillator in which the temporal variation of the concentrations of mRNA (<i>M</i>) and the various forms of clock protein, cytosolic (<i>P₀</i>, <i>P₁</i>, <i>P₂</i>) or nuclear (<i>P_n</i>), are governed by the system of kinetics equations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.e001" target="_blank">1</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.e005" target="_blank">5</a>. The associated parameters with their specific values are indicated in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.s001" target="_blank">S1 Table</a> in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.s001" target="_blank">S1 File</a>. This scheme is similar to the one presented in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115067#pone.0115067.ref006" target="_blank">6</a>].</p

Dependence of the period (<i>τ</i>) with <i>k_s</i>, <i>K_r</i> and <i>V_r</i> for <i>nH</i> = 1.

<p>(<i>A</i>) The <i>τ</i> values are shown in pseudocolor within the <i>K_r</i>-<i>V_r</i>-subspace for different values of the <i>k_s</i> parameter, from <i>0</i> (<i>left</i>) to 2 <i>h</i>^−<i>1</i> (<i>right</i>). Infradian (<i>τ</i> ≥ 28 <i>h</i>) are predominant for <i>k_s</i> values < 2 <i>h</i>^−<i>1</i>. For each <i>k_s</i> value, the range of <i>τ</i> values is narrower than those observed for <i>nH</i> = 4 (the color key for <i>τ</i> is at the bottom of the plot). Black areas indicate zones in which there are damped oscillations. A white dotted line was added in order to emphasize the transition between the two dynamical behaviors observed in our model. (<i>B</i>) An inset of the <i>K_r</i>-<i>V_r</i>-space shown in panel <i>A</i> for <i>k_s</i> = 2 <i>h</i>^−<i>1</i> (<i>right</i>) shows how <i>τ</i> changes within the circadian range; nevertheless the extent of <i>τ</i> change is smaller than that observed for <i>nH</i> = 4. Note that the key color was rescaled in order to display the differences in more detail (<i>C</i>) Dependence of <i>τ</i> (<i>red line</i>) with <i>V_r</i> for a fixed value of <i>K_r</i> = 0.01 <i>nM</i>. The black line shows the pseudo-period value for damped oscillations.</p