Structure of PTB bound to RNA: specific binding and implications for splicing regulation     

Oberstrass FC  Auweter SD  Erat M  Hargous Y  Henning A  Wenter P  Reymond L  Amir-Ahmady B  Pitsch S  Black DL  Allain FH 《Science (New York, N.Y.)》2005,309(5743):2054-2057

The polypyrimidine tract binding protein (PTB) is a 58-kilodalton RNA binding protein involved in multiple aspects of messenger RNA metabolism, including the repression of alternative exons. We have determined the solution structures of the four RNA binding domains (RBDs) of PTB, each bound to a CUCUCU oligonucleotide. Each RBD binds RNA with a different binding specificity. RBD3 and RBD4 interact, resulting in an antiparallel orientation of their bound RNAs. Thus, PTB will induce RNA looping when bound to two separated pyrimidine tracts within the same RNA. This leads to structural models for how PTB functions as an alternative-splicing repressor.  相似文献   

The chemistry of sexual deception in an orchid-wasp pollination system     

Schiestl FP  Peakall R  Mant JG  Ibarra F  Schulz C  Franke S  Francke W 《Science (New York, N.Y.)》2003,302(5644):437-438

The "sexually deceptive" orchid Chiloglottis trapeziformis attracts males of its pollinator species, the thynnine wasp Neozeleboria cryptoides, by emitting a unique volatile compound, 2-ethyl-5-propylcyclohexan-1,3-dione, which is also produced by female wasps as a male-attracting sex pheromone.  相似文献   

Pattern-oriented modeling of agent-based complex systems: lessons from ecology   总被引：6，自引：0，他引：6  

Grimm V  Revilla E  Berger U  Jeltsch F  Mooij WM  Railsback SF  Thulke HH  Weiner J  Wiegand T  DeAngelis DL 《Science (New York, N.Y.)》2005,310(5750):987-991

Agent-based complex systems are dynamic networks of many interacting agents; examples include ecosystems, financial markets, and cities. The search for general principles underlying the internal organization of such systems often uses bottom-up simulation models such as cellular automata and agent-based models. No general framework for designing, testing, and analyzing bottom-up models has yet been established, but recent advances in ecological modeling have come together in a general strategy we call pattern-oriented modeling. This strategy provides a unifying framework for decoding the internal organization of agent-based complex systems and may lead toward unifying algorithmic theories of the relation between adaptive behavior and system complexity.  相似文献   

Mutations in dynein link motor neuron degeneration to defects in retrograde transport     

Hafezparast M  Klocke R  Ruhrberg C  Marquardt A  Ahmad-Annuar A  Bowen S  Lalli G  Witherden AS  Hummerich H  Nicholson S  Morgan PJ  Oozageer R  Priestley JV  Averill S  King VR  Ball S  Peters J  Toda T  Yamamoto A  Hiraoka Y  Augustin M  Korthaus D  Wattler S  Wabnitz P  Dickneite C  Lampel S  Boehme F  Peraus G  Popp A  Rudelius M  Schlegel J  Fuchs H  Hrabe de Angelis M  Schiavo G  Shima DT  Russ AP  Stumm G  Martin JE  Fisher EM 《Science (New York, N.Y.)》2003,300(5620):808-812

Degenerative disorders of motor neurons include a range of progressive fatal diseases such as amyotrophic lateral sclerosis (ALS), spinal-bulbar muscular atrophy (SBMA), and spinal muscular atrophy (SMA). Although the causative genetic alterations are known for some cases, the molecular basis of many SMA and SBMA-like syndromes and most ALS cases is unknown. Here we show that missense point mutations in the cytoplasmic dynein heavy chain result in progressive motor neuron degeneration in heterozygous mice, and in homozygotes this is accompanied by the formation of Lewy-like inclusion bodies, thus resembling key features of human pathology. These mutations exclusively perturb neuron-specific functions of dynein.  相似文献   

Thymine dimerization in DNA is an ultrafast photoreaction     

Schreier WJ  Schrader TE  Koller FO  Gilch P  Crespo-Hernández CE  Swaminathan VN  Carell T  Zinth W  Kohler B 《Science (New York, N.Y.)》2007,315(5812):625-629

Femtosecond time-resolved infrared spectroscopy was used to study the formation of cyclobutane dimers in the all-thymine oligodeoxynucleotide (dT)18 by ultraviolet light at 272 nanometers. The appearance of marker bands in the time-resolved spectra indicates that the dimers are fully formed approximately 1 picosecond after ultraviolet excitation. The ultrafast appearance of this mutagenic photolesion points to an excited-state reaction that is approximately barrierless for bases that are properly oriented at the instant of light absorption. The low quantum yield of this photoreaction is proposed to result from infrequent conformational states in the unexcited polymer, revealing a strong link between conformation before light absorption and photodamage.  相似文献   

The Air noncoding RNA epigenetically silences transcription by targeting G9a to chromatin   总被引：1，自引：0，他引：1  

Nagano T  Mitchell JA  Sanz LA  Pauler FM  Ferguson-Smith AC  Feil R  Fraser P 《Science (New York, N.Y.)》2008,322(5908):1717-1720

  相似文献   

Secondary siRNAs result from unprimed RNA synthesis and form a distinct class   总被引：1，自引：0，他引：1  

Sijen T  Steiner FA  Thijssen KL  Plasterk RH 《Science (New York, N.Y.)》2007,315(5809):244-247

In Caenorhabditis elegans, an effective RNA interference (RNAi) response requires the production of secondary short interfering RNAs (siRNAs) by RNA-directed RNA polymerases (RdRPs). We cloned secondary siRNAs from transgenic C. elegans lines expressing a single 22-nucleotide primary siRNA. Several secondary siRNAs start a few nucleotides downstream of the primary siRNA, indicating that non-RISC (RNA-induced silencing complex)-cleaved mRNAs are substrates for secondary siRNA production. In lines expressing primary siRNAs with single-nucleotide mismatches, secondary siRNAs do not carry the mismatch but contain the nucleotide complementary to the mRNA. We infer that RdRPs perform unprimed RNA synthesis. Secondary siRNAs are only of antisense polarity, carry 5' di- or triphosphates, and are only in the minority associated with RDE-1, the RNAi-specific Argonaute protein. Therefore, secondary siRNAs represent a distinct class of small RNAs. Their biogenesis depends on RdRPs, and we propose that each secondary siRNA is an individual RdRP product.  相似文献   

Glutamatergic and dopaminergic neurons mediate anxiogenic and anxiolytic effects of CRHR1     

Refojo D  Schweizer M  Kuehne C  Ehrenberg S  Thoeringer C  Vogl AM  Dedic N  Schumacher M  von Wolff G  Avrabos C  Touma C  Engblom D  Schütz G  Nave KA  Eder M  Wotjak CT  Sillaber I  Holsboer F  Wurst W  Deussing JM 《Science (New York, N.Y.)》2011,333(6051):1903-1907

The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid-containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.  相似文献   

Compared effects of long-term pig slurry applications and mineral fertilization on soil denitrification and its end products (N2O, N2)     

Christophe Dambreville  Catherine Hénault  Florian Bizouard  Thierry Morvan  Rémi Chaussod  Jean-Claude Germon 《Biology and Fertility of Soils》2006,42(6):490-500

The long-term (9 years) effect of pig slurry applications vs mineral fertilization on denitrifying activity, N₂O production and soil organic carbon (C) (extractable C, microbial biomass C and total organic C) was compared at three soil depths of adjacent plots. The denitrifying activities were measured on undisturbed soil cores and on sieved soil samples with acetylene method to estimate denitrification rates under field or potential conditions. Pig slurry applications had a moderate impact on the C pools. Total organic C was increased by +6.5% and microbial biomass C by ≥25%. The potential denitrifying activity on soil suspension was stimulated (×1.8, P<0.05) 12 days after the last slurry application. This stimulation was still apparent, but not significant, 10 months later and, according to both methods of denitrifying activity measurement (r ²=0.916, P<0.01 on sieved soil; r ²=0.845, P<0.001 on soil cores), was associated with an increase in microbial biomass C above a threshold of about 105 mg kg⁻¹. The effect of pig slurry on denitrification and N₂O reduction rates was detected on the surface layer (0–20 cm) only. However, no pig slurry effect could be detected on soil cores at field conditions or after NO₃ ⁻ enrichments at 20°C. Although the potential denitrifying activity in sieved soil samples was stimulated, the N₂O production was lower (P<0.03) in the plot fertilized with pig slurry, indicating a lower N₂O/(N₂O + N₂) ratio of the released gases. The pig-slurry-fertilized plot also showed a higher N₂O reduction activity, which is coherent with the lower N₂O production in anaerobiosis.  相似文献   

Ecological-genetic investigations in environmentally stressed mature sugar maple (Acer saccharum marsh.) populations     

T H. Geburek  P. Knowles 《Water, air, and soil pollution》1992,62(3-4):261-268

In six mature, environmentally stressed sugar maple (Acer saccharum) populations totalling 350 trees, genetic structures were studied within stands. Genetic variation was electrophoretically analyzed for 12 enzyme systems. The populations revealed Hardy-Weinberg proportions for all 11 polymorphic loci. Observed and conditional heterozygosity were. 141 and 899, respectively. Analysis of fixation indices indicated a slight heterozygote deficiency compared to panmictic conditions. Population differentiation was weak (F _ST =.017). Between healthy and declining subpopulations no significant differences were detected in terms of allozyme variation. However in healthy trees, conditional heterozygosity (H _c) and relative genotypic multiplicity (M _rel) were higher in five out of six populations.  相似文献