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121.
Kitagawa D Vakonakis I Olieric N Hilbert M Keller D Olieric V Bortfeld M Erat MC Flückiger I Gönczy P Steinmetz MO 《Cell》2011,144(3):364-375
The centriole, and the related basal body, is an ancient organelle characterized by a universal 9-fold radial symmetry and is critical for generating cilia, flagella, and centrosomes. The mechanisms directing centriole formation are incompletely understood and represent a fundamental open question in biology. Here, we demonstrate that the centriolar protein SAS-6 forms rod-shaped homodimers that interact through their N-terminal domains to form oligomers. We establish that such oligomerization is essential for centriole formation in C. elegans and human cells. We further generate a structural model of the related protein Bld12p from C. reinhardtii, in which nine homodimers assemble into a ring from which nine coiled-coil rods radiate outward. Moreover, we demonstrate that recombinant Bld12p self-assembles into structures akin to the central hub of the cartwheel, which serves as a scaffold for centriole formation. Overall, our findings establish a structural basis for the universal 9-fold symmetry of centrioles. 相似文献
122.
Delphine Lapaillerie Benoît Lelandais Eric Mauro Floriane Lagadec Camille Tumiotto Csaba Miskey Guillaume Ferran Natacha Kuschner Christina Calmels Mathieu Mtifiot Caroline Rooryck Zoltan Ivics Marc Ruff Christophe Zimmer Paul Lesbats Jrme Toutain Vincent Parissi 《Nucleic acids research》2021,49(19):11241
The stable insertion of the retroviral genome into the host chromosomes requires the association between integration complexes and cellular chromatin via the interaction between retroviral integrase and the nucleosomal target DNA. This final association may involve the chromatin-binding properties of both the retroviral integrase and its cellular cofactor LEDGF/p75. To investigate this and better understand the LEDGF/p75-mediated chromatin tethering of HIV-1 integrase, we used a combination of biochemical and chromosome-binding assays. Our study revealed that retroviral integrase has an intrinsic ability to bind and recognize specific chromatin regions in metaphase even in the absence of its cofactor. Furthermore, this integrase chromatin-binding property was modulated by the interaction with its cofactor LEDGF/p75, which redirected the enzyme to alternative chromosome regions. We also better determined the chromatin features recognized by each partner alone or within the functional intasome, as well as the chronology of efficient LEDGF/p75-mediated targeting of HIV-1 integrase to chromatin. Our data support a new chromatin-binding function of integrase acting in concert with LEDGF/p75 for the optimal association with the nucleosomal substrate. This work also provides additional information about the behavior of retroviral integration complexes in metaphase chromatin and the mechanism of action of LEDGF/p75 in this specific context. 相似文献
123.
What is the benefit to Escherichia coli of having multiple toxin-antitoxin systems in its genome? 总被引:3,自引:0,他引:3
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Tsilibaris V Maenhaut-Michel G Mine N Van Melderen L 《Journal of bacteriology》2007,189(17):6101-6108
The Escherichia coli K-12 chromosome encodes at least five proteic toxin-antitoxin (TA) systems. The mazEF and relBE systems have been extensively characterized and were proposed to be general stress response modules. On one hand, mazEF was proposed to act as a programmed cell death system that is triggered by a variety of stresses. On the other hand, relBE and mazEF were proposed to serve as growth modulators that induce a dormancy state during amino acid starvation. These conflicting hypotheses led us to test a possible synergetic effect of the five characterized E. coli TA systems on stress response. We compared the behavior of a wild-type strain and its derivative devoid of the five TA systems under various stress conditions. We were unable to detect TA-dependent programmed cell death under any of these conditions, even under conditions previously reported to induce it. Thus, our results rule out the programmed-cell-death hypothesis. Moreover, the presence of the five TA systems advantaged neither recovery from the different stresses nor cell growth under nutrient-limited conditions in competition experiments. This casts a doubt on whether TA systems significantly influence bacterial fitness and competitiveness during non-steady-state growth conditions. 相似文献
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125.
Bossu C Galusca B Normand S Germain N Collet P Frere D Lang F Laville M Estour B 《American journal of physiology. Endocrinology and metabolism》2007,292(1):E132-E137
Constitutional thinness (CT) is characterized by a low and stable body mass index (BMI) without any hormonal abnormality. To understand the weight steadiness, energetic metabolism was evaluated. Seven CT, seven controls, and six anorexia nervosa (AN) young women were compared. CT and AN had a BMI <16.5 kg/m(2). Four criteria were evaluated: 1) energy balance including diet record, resting metabolic rate (RMR) (indirect calorimetry), total energy expenditure (TEE) (doubly labeled water), physical activity; 2) body composition (dual-energy X-ray absorptiometry); 3) biological markers (leptin, IGF-I, free T3); 4) psychological profile of eating behavior. The normality of free T3 (3.7 +/- 0.5 pmol/l), IGF-I (225 +/- 93 ng/ml), and leptin (8.3 +/- 3.4 ng/ml) confirmed the absence of undernutrition in CT. Their psychological profiles revealed a weight gain desire. TEE (kJ/day) in CT (8,382 +/- 988) was not found significantly different from that of controls (8,793 +/- 845) and AN (8,001 +/- 2,152). CT food intake (7,565 +/- 908 kJ/day) was found similar to that of controls (7,961 +/- 1,452 kJ/day) and higher than in AN (4,894 +/- 703 kJ/day), thus explaining the energy metabolism balance. Fat-free mass (FFM) (kg) was similar in CT and AN (32.5 +/- 2.9 vs. 34.1 +/- 1.9) and higher in controls (37.8 +/- 1.6). While RMR absolute values (kJ/day) were lower in CT (4,839 +/- 473) than in controls (5,576 +/- 209), RMR values adjusted for FFM were the highest in CT. TEE-to-FFM ratio was also higher in CT than in controls. Energetic metabolism balance maintains a stable low weight in CT. An increased energy expenditure-to-FFM ratio differentiates CT from controls and could account for the resistance to weight gain observed in CT. 相似文献
126.
This paper reviews the major achievements of the preschool years regarding language acquisition. Although most children appear to master their native language with little apparent effort, learning a language is a complex task. It requires the ability to extract clues from environmental stimuli and to discover how those stimuli convey meanings and are modified according to the meaning conveyed. In general, language learning follows a similar sequence regardless of the language being learned. The major accomplishments in the areas of speech perception, early sound production, phonology, lexicon, syntax, and morphology are described, with specific examples from recent studies of acquisition of French in young children from Québec. These examples confirm major milestones observed in other languages, but also illustrate how comparisons across languages and across children learning the same language can be challenging. For each area, current issues are identified regarding the bases (neurological, genetic) of language development, as well as the processes (social, cognitive, linguistic) involved. Current hypotheses regarding language acquisition and language disorders are briefly discussed. 相似文献
127.
128.
Anna Delprato Yasmine Al Kadri Natacha Pérébaskine Cécile Monfoulet Yves Henry Anthony K. Henras Sébastien Fribourg 《Nucleic acids research》2014,42(15):10161-10172
The essential Rcl1p and Bms1p proteins form a complex required for 40S ribosomal subunit maturation. Bms1p is a GTPase and Rcl1p has been proposed to catalyse the endonucleolytic cleavage at site A2 separating the pre-40S and pre-60S maturation pathways. We determined the 2.0 Å crystal structure of Bms1p associated with Rcl1p. We demonstrate that Rcl1p nuclear import depends on Bms1p and that the two proteins are loaded into pre-ribosomes at a similar stage of the maturation pathway and remain present within pre-ribosomes after cleavage at A2. Importantly, GTP binding to Bms1p is not required for the import in the nucleus nor for the incorporation of Rcl1p into pre-ribosomes, but is essential for early pre-rRNA processing. We propose that GTP binding to Bms1p and/or GTP hydrolysis may induce conformational rearrangements within the Bms1p-Rcl1p complex allowing the interaction of Rcl1p with its RNA substrate. 相似文献
129.
Silvia Ramundo David Casero Timo Mühlhaus Dorothea Hemme Frederik Sommer Michèle Crèvecoeur Michèle Rahire Michael Schroda Jannette Rusch Ursula Goodenough Matteo Pellegrini Maria Esther Perez-Perez José Luis Crespo Olivier Schaad Natacha Civic Jean David Rochaix 《The Plant cell》2014,26(5):2201-2222
130.
Natacha Turck Xavier Robin Nadia Walter Catherine Fouda Alexandre Hainard Roman Sztajzel Ghislaine Wagner Denis F. Hochstrasser Joan Montaner Pierre R. Burkhard Jean-Charles Sanchez 《PloS one》2012,7(9)