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eIF4EBP3L Acts as a Gatekeeper of TORC1 In Activity-Dependent Muscle Growth by Specifically Regulating Mef2ca Translational Initiation  [PDF]
Orli Yogev,Victoria C. Williams,Yaniv Hinits,Simon M. Hughes
PLOS Biology , 2013, DOI: 10.1371/journal.pbio.1001679
Abstract: Muscle fiber size is activity-dependent and clinically important in ageing, bed-rest, and cachexia, where muscle weakening leads to disability, prolonged recovery times, and increased costs. Inactivity causes muscle wasting by triggering protein degradation and may simultaneously prevent protein synthesis. During development, muscle tissue grows by several mechanisms, including hypertrophy of existing fibers. As in other tissues, the TOR pathway plays a key role in promoting muscle protein synthesis by inhibition of eIF4EBPs (eukaryotic Initiation Factor 4E Binding Proteins), regulators of the translational initiation. Here, we tested the role of TOR-eIF4EBP in a novel zebrafish muscle inactivity model. Inactivity triggered up-regulation of eIF4EBP3L (a zebrafish homolog of eIF4EBP3) and diminished myosin and actin content, myofibrilogenesis, and fiber growth. The changes were accompanied by preferential reduction of the muscle transcription factor Mef2c, relative to Myod and Vinculin. Polysomal fractionation showed that Mef2c decrease was due to reduced translation of mef2ca mRNA. Loss of Mef2ca function reduced normal muscle growth and diminished the reduction in growth caused by inactivity. We identify eIF4EBP3L as a key regulator of Mef2c translation and protein level following inactivity; blocking eIF4EBP3L function increased Mef2ca translation. Such blockade also prevented the decline in mef2ca translation and level of Mef2c and slow myosin heavy chain proteins caused by inactivity. Conversely, overexpression of active eIF4EBP3L mimicked inactivity by decreasing the proportion of mef2ca mRNA in polysomes, the levels of Mef2c and slow myosin heavy chain, and myofibril content. Inhibiting the TOR pathway without the increase in eIF4EBP3L had a lesser effect on myofibrilogenesis and muscle size. These findings identify eIF4EBP3L as a key TOR-dependent regulator of muscle fiber size in response to activity. We suggest that by selectively inhibiting translational initiation of mef2ca and other mRNAs, eIF4EBP3L reprograms the translational profile of muscle, enabling it to adjust to new environmental conditions.
Global analyses of mRNA translational control during early Drosophila embryogenesis
Xiaoli Qin, Soyeon Ahn, Terence P Speed, Gerald M Rubin
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-4-r63
Abstract: We determined ribosomal density and ribosomal occupancy of over 10,000 transcripts during the first ten hours after egg laying.We report the extent and general nature of gene regulation at the translational level during early Drosophila embryogenesis on a genome-wide basis. The diversity of the translation profiles indicates multiple mechanisms modulating transcript-specific translation. Cluster analyses suggest that the genes involved in some biological processes are co-regulated at the translational level at certain developmental stages.In many animal species, the first few hours of life proceed with little or no transcription, and regulation of developmental events at these early stages is conferred by maternal cytoplasm rather than transcriptional activity in the zygotic nucleus. During the first two hours after fertilization, Drosophila embryos undergo 13 zygotic division cycles (Bownes' stages 1-4) and are syncytial in that the nuclei divide in a common cytoplasm without cytokenesis, except that pole cells, precursors to germline, are segregated in cycle 10. Synthesis of rRNA, tRNAs, 5S RNAs, snRNAs, poly(A)+ RNAs, and histone mRNAs is not detectable until cycle 11 or 12. Both spatial control and temporal control of mRNA translation are implemented in the early patterning of the Drosophila embryo. The basic embryonic body plan, defined by both anterior-posterior and dorso-ventral axes, as well as precursors for terminal structures, relies on the regulation of mRNA localization and coupled regulation of mRNA translation. Complete inhibition of protein synthesis with translation inhibitors, for example, cycloheximide, puromycin or pactamycin, quickly and entirely blocks mitotic cycles and arrests development [1,2]. After zygotic transcription begins at mitotic cycle 13 (about 1.5-2 hours after fertilization), the efficient use of zygotic transcripts depends on the degradation of maternal mRNA after fertilization [3].The modulation of translation can be exerted b
Translational Profiling of Clock Cells Reveals Circadianly Synchronized Protein Synthesis  [PDF]
Yanmei Huang ,Joshua A. Ainsley,Leon G. Reijmers,F. Rob Jackson
PLOS Biology , 2013, DOI: 10.1371/journal.pbio.1001703
Abstract: Genome-wide studies of circadian transcription or mRNA translation have been hindered by the presence of heterogeneous cell populations in complex tissues such as the nervous system. We describe here the use of a Drosophila cell-specific translational profiling approach to document the rhythmic “translatome” of neural clock cells for the first time in any organism. Unexpectedly, translation of most clock-regulated transcripts—as assayed by mRNA ribosome association—occurs at one of two predominant circadian phases, midday or mid-night, times of behavioral quiescence; mRNAs encoding similar cellular functions are translated at the same time of day. Our analysis also indicates that fundamental cellular processes—metabolism, energy production, redox state (e.g., the thioredoxin system), cell growth, signaling and others—are rhythmically modulated within clock cells via synchronized protein synthesis. Our approach is validated by the identification of mRNAs known to exhibit circadian changes in abundance and the discovery of hundreds of novel mRNAs that show translational rhythms. This includes Tdc2, encoding a neurotransmitter synthetic enzyme, which we demonstrate is required within clock neurons for normal circadian locomotor activity.
Biodegradation of Trichloroethylene (TCE) in the Presence of Phenolic Compound  [PDF]
Muhammad Ferhan
Journal of Biological Sciences , 2003,
Abstract: Experimental bioreactors operated as closed recirculation systems were inoculated with aerobic bacterial cultures that utilized tryptone–yeast extract as carbon and energy sources. These were inoculated with the bacterial culture, which degraded trichloroethylene (TCE) and was observed after 5 days of incubation. Each bioreactor consisted of an expanded bed column through which the liquid phase was recirculated. TCE degradation was also observed with the metabolism of aromatic hydrocarbons established for indigenous microbial population in soil and ground water, in which TCE removal has been shown to be stimulated by the addition of phenol. So co-metabolism occurred when a non-specific enzyme or co-factor was used to transform the growth supporting carbon source, also capable of degrading non-growth supporting compounds. Gas chromatography was use to monitor TCE and their metabolites which compare to run their standards and to check their retention time (tr) values. The retention time (tr) values of phenol, catechol, TCA, TCE were 7.22, 8.82, 8.55 and 2.25.
高锰酸钾去除水中TCE的研究  [PDF]
田璐,杨琦,尚海涛,郝春博
环境科学 , 2009,
Abstract: 以水中常见的氯代烃污染物三氯乙烯(TCE)为目标污染物,以自制的高锰酸钾溶液为氧化剂,探讨了不同条件下高锰酸钾对TCE的去除效果.结果表明,在30℃、高锰酸钾浓度为0.276g·L-1的条件下,反应时间为30 min时,TCE的去除率就可达到100%.高锰酸钾对TCE的去除符合一级反应动力学方程,速率常数为0.1429min-1,半衰期t1/2为4.85 min.TCE的去除速率随高锰酸钾浓度的增大而增大并呈线性关系,随反应温度的升高而增大,受pH值和离子强度的影响较小.
过硫酸钾去除水中的TCE  [PDF]
王诗宗,杨琦,田璐
环境工程学报 , 2013,
Abstract: 以地水中的氯代烃污染物三氯乙烯(TCE)为目标污染物,以过硫酸钾溶液为氧化剂,探讨了不同条件下过硫酸钾对TCE的去除效果。实验结果表明,在40℃,过硫酸钾初始浓度为2.43g/L条件下,反应2h后,TCE的去除率就可达到96.8%;过硫酸钾对TCE的去除符合一级反应动力学方程,速率常数(K)为1.3364h-1,半衰期(t1/2)为0.51h;过硫酸钾对TCE的去除速率在pH为中性附近时最大,其后无论pH升高或降低去除速率均减小;受温度和pH影响较明显,并且反应温度越高,受pH的影响越明显;随离子强度的增加而减小;反应活化能为119.6kJ/mol;过硫酸钾溶于水生成过硫酸根离子(S2O82-),S2O82-会进一步生成硫酸根自由基(SO4-·),在碱性条件下,SO4-·与OH-反应会进一步生成羟基自由基(·OH)。过硫酸钾对于TCE的去除主要源自SO4-·和·OH的强氧化性。
Application of terpene-induced cell for enhancing biodegradation of TCE contaminated soil  [PDF]
Oramas Suttinun,Peter B. Lederman,Ekawan Luepromchai
Songklanakarin Journal of Science and Technology , 2004,
Abstract: Trichloroethylene (TCE), a chlorinated solvent, is a major water pollutant originating from spillage and inappropriate disposal of dry cleaning agents, degreasing solvents, and paint strippers. Due to its widespread contamination and potential health threat, remediation technology to clean-up TCE is necessary. Aerobic biodegradation of TCE is reported to occur via cometabolism, by which TCE degrading bacteria utilize other compounds such as toluene, phenol, and methane as growth substrate and enzyme inducer. Although toluene is reported to be the most effective inducer, it is regulated as a hazardous material and should not be applied to the environment. The objectives of this study were to identify an alternative enzyme inducer as well as to apply the induced bacteria for degradation of TCE in contaminated soil. We investigated the effect of terpenes, the main components in volatile essential oils of plants, on induction of TCE degradation in Rhodococcus gordoniae P3, a local Gram (+) bacterium. Selected terpenes including cumene, limonene, carvone and pinene at various concentrations were used in the study. Results from liquid culture showed that 25 mg l-1 cumeneinduced R. gordoniae P3 cells resulted in 75% degradation of 10 ppm TCE within 24 hrs. Soil microcosms were later employed to investigate the ability of cumene to enhance TCE biodegradation in the environment. There were two bioremediation treatments studied, including bioaugmentation, the inoculation of cumeneinduced R. gordoniae P3, and biostimulation, the addition of cumene to induce soil indigenous microorganisms to degrade TCE. Bioaugmentation and biostimulation were shown to accelerate TCE reduction significantly more than control treatment at the beginning of study. The results suggest that cumene-induced R. gordoniae P3 and cumene can achieve rapid TCE biodegradation.
Therapeutic ultrasound as a potential male contraceptive: power, frequency and temperature required to deplete rat testes of meiotic cells and epididymides of sperm determined using a commercially available system
James K Tsuruta, Paul A Dayton, Caterina M Gallippi, Michael G O'Rand, Michael A Streicker, Ryan C Gessner, Thomas S Gregory, Erick JR Silva, Katherine G Hamil, Glenda J Moser, David C Sokal
Reproductive Biology and Endocrinology , 2012, DOI: 10.1186/1477-7827-10-7
Abstract: Sprague-Dawley rats were anesthetized and their testes were treated with 1 MHz or 3 MHz ultrasound while varying power, duration and temperature of treatment.We found that 3 MHz ultrasound delivered with 2.2 Watt per square cm power for fifteen minutes was necessary to deplete spermatocytes and spermatids from the testis and that this treatment significantly reduced epididymal sperm reserves. 3 MHz ultrasound treatment reduced total epididymal sperm count 10-fold lower than the wet-heat control and decreased motile sperm counts 1,000-fold lower than wet-heat alone. The current treatment regimen provided nominally more energy to the treatment chamber than Fahim's originally reported conditions of 1 MHz ultrasound delivered at 1 Watt per square cm for ten minutes. However, the true spatial average intensity, effective radiating area and power output of the transducers used by Fahim were not reported, making a direct comparison impossible. We found that germ cell depletion was most uniform and effective when we rotated the therapeutic transducer to mitigate non-uniformity of the beam field. The lowest sperm count was achieved when the coupling medium (3% saline) was held at 37 degrees C and two consecutive 15-minute treatments of 3 MHz ultrasound at 2.2 Watt per square cm were separated by 2 days.The non-invasive nature of ultrasound and its efficacy in reducing sperm count make therapeutic ultrasound a promising candidate for a male contraceptive. However, further studies must be conducted to confirm its efficacy in providing a contraceptive effect, to test the result of repeated use, to verify that the contraceptive effect is reversible and to demonstrate that there are no detrimental, long-term effects from using ultrasound as a method of male contraception.An ideal male contraceptive would be inexpensive, reliable and reversible. Other desirable qualities include a low incidence of side effects, prolonged duration of the contraceptive effect and no need for invasiv
Phosphorylation of a Central Clock Transcription Factor Is Required for Thermal but Not Photic Entrainment  [PDF]
Euna Lee equal contributor,Eun Hee Jeong equal contributor,Hyun-Jeong Jeong,Evrim Yildirim,Jens T. Vanselow,Fanny Ng,Yixiao Liu,Guruswamy Mahesh,Achim Kramer,Paul E. Hardin,Isaac Edery ,Eun Young Kim
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004545
Abstract: Transcriptional/translational feedback loops drive daily cycles of expression in clock genes and clock-controlled genes, which ultimately underlie many of the overt circadian rhythms manifested by organisms. Moreover, phosphorylation of clock proteins plays crucial roles in the temporal regulation of clock protein activity, stability and subcellular localization. dCLOCK (dCLK), the master transcription factor driving cyclical gene expression and the rate-limiting component in the Drosophila circadian clock, undergoes daily changes in phosphorylation. However, the physiological role of dCLK phosphorylation is not clear. Using a Drosophila tissue culture system, we identified multiple phosphorylation sites on dCLK. Expression of a mutated version of dCLK where all the mapped phospho-sites were switched to alanine (dCLK-15A) rescues the arrythmicity of Clkout flies, yet with an approximately 1.5 hr shorter period. The dCLK-15A protein attains substantially higher levels in flies compared to the control situation, and also appears to have enhanced transcriptional activity, consistent with the observed higher peak values and amplitudes in the mRNA rhythms of several core clock genes. Surprisingly, the clock-controlled daily activity rhythm in dCLK-15A expressing flies does not synchronize properly to daily temperature cycles, although there is no defect in aligning to light/dark cycles. Our findings suggest a novel role for clock protein phosphorylation in governing the relative strengths of entraining modalities by adjusting the dynamics of circadian gene expression.
Translational Control by the DEAD Box RNA Helicase belle Regulates Ecdysone-Triggered Transcriptional Cascades  [PDF]
Robert J. Ihry,Anne L. Sapiro,Arash Bashirullah
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1003085
Abstract: Steroid hormones act, through their respective nuclear receptors, to regulate target gene expression. Despite their critical role in development, physiology, and disease, however, it is still unclear how these systemic cues are refined into tissue-specific responses. We identified a mutation in the evolutionarily conserved DEAD box RNA helicase belle/DDX3 that disrupts a subset of responses to the steroid hormone ecdysone during Drosophila melanogaster metamorphosis. We demonstrate that belle directly regulates translation of E74A, an ets transcription factor and critical component of the ecdysone-induced transcriptional cascade. Although E74A mRNA accumulates to abnormally high levels in belle mutant tissues, no E74A protein is detectable, resulting in misregulation of E74A-dependent ecdysone response genes. The accumulation of E74A mRNA in belle mutant salivary glands is a result of auto-regulation, fulfilling a prediction made by Ashburner nearly 40 years ago. In this model, Ashburner postulates that, in addition to regulating secondary response genes, protein products of primary response genes like E74A also inhibit their own ecdysone-induced transcription. Moreover, although ecdysone-triggered transcription of E74A appears to be ubiquitous during metamorphosis, belle-dependent translation of E74A mRNA is spatially restricted. These results demonstrate that translational control plays a critical, and previously unknown, role in refining transcriptional responses to the steroid hormone ecdysone.
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