Inhibition of the complement cascade by the major secretory protein of vaccinia virus   总被引：28，自引：0，他引：28  

G J Kotwal  S N Isaacs  R McKenzie  M M Frank  B Moss 《Science (New York, N.Y.)》1990,250(4982):827-830

The complement system contributes to host defenses against invasion by infectious agents. A 35-kilodalton protein, encoded by vaccinia virus and secreted from infected cells, has sequence similarities to members of a gene family that includes complement control proteins. Biochemical and genetic studies showed that the viral protein binds to derivatives of the fourth component of complement and inhibits the classical complement cascade, suggesting that it serves as a defense molecule to help the virus evade the consequences of complement activation.  相似文献   

Eco1-dependent cohesin acetylation during establishment of sister chromatid cohesion     

Rolef Ben-Shahar T  Heeger S  Lehane C  East P  Flynn H  Skehel M  Uhlmann F 《Science (New York, N.Y.)》2008,321(5888):563-566

Replicated chromosomes are held together by the chromosomal cohesin complex from the time of their synthesis in S phase onward. This requires the replication fork-associated acetyl transferase Eco1, but Eco1's mechanism of action is not known. We identified spontaneous suppressors of the thermosensitive eco1-1 allele in budding yeast. An acetylation-mimicking mutation of a conserved lysine in cohesin's Smc3 subunit makes Eco1 dispensable for cell growth, and we show that Smc3 is acetylated in an Eco1-dependent manner during DNA replication to promote sister chromatid cohesion. A second set of eco1-1 suppressors inactivate the budding yeast ortholog of the cohesin destabilizer Wapl. Our results indicate that Eco1 modifies cohesin to stabilize sister chromatid cohesion in parallel with a cohesion establishment reaction that is in principle Eco1-independent.  相似文献   

Evolution of supergene families associated with insecticide resistance   总被引：5，自引：0，他引：5  

Ranson H  Claudianos C  Ortelli F  Abgrall C  Hemingway J  Sharakhova MV  Unger MF  Collins FH  Feyereisen R 《Science (New York, N.Y.)》2002,298(5591):179-181

The emergence of insecticide resistance in the mosquito poses a serious threat to the efficacy of many malaria control programs. We have searched the Anopheles gambiae genome for members of the three major enzyme families- the carboxylesterases, glutathione transferases, and cytochrome P450s-that are primarily responsible for metabolic resistance to insecticides. A comparative genomic analysis with Drosophila melanogaster reveals that a considerable expansion of these supergene families has occurred in the mosquito. Low gene orthology and little chromosomal synteny paradoxically contrast the easily identified orthologous groups of genes presumably seeded by common ancestors. In A. gambiae, the independent expansion of paralogous genes is mainly a consequence of the formation of clusters among locally duplicated genes. These expansions may reflect the functional diversification of supergene families consistent with major differences in the life history and ecology of these organisms. These data provide a basis for identifying the resistance-associated enzymes within these families. This will enable the resistance status of mosquitoes, flies, and possibly other holometabolous insects to be monitored. The analyses also provide the means for identifying previously unknown molecules involved in fundamental biological processes such as development.  相似文献   

Structure, function, and activator-induced conformations of the CRSP coactivator     

Taatjes DJ  Näär AM  Andel F  Nogales E  Tjian R 《Science (New York, N.Y.)》2002,295(5557):1058-1062

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Resting microglial cells are highly dynamic surveillants of brain parenchyma in vivo   总被引：1，自引：0，他引：1  

Nimmerjahn A  Kirchhoff F  Helmchen F 《Science (New York, N.Y.)》2005,308(5726):1314-1318

Microglial cells represent the immune system of the mammalian brain and therefore are critically involved in various injuries and diseases. Little is known about their role in the healthy brain and their immediate reaction to brain damage. By using in vivo two-photon imaging in neocortex, we found that microglial cells are highly active in their presumed resting state, continually surveying their microenvironment with extremely motile processes and protrusions. Furthermore, blood-brain barrier disruption provoked immediate and focal activation of microglia, switching their behavior from patroling to shielding of the injured site. Microglia thus are busy and vigilant housekeepers in the adult brain.  相似文献   

CO2-forced climate and vegetation instability during Late Paleozoic deglaciation     

Montañez IP  Tabor NJ  Niemeier D  Dimichele WA  Frank TD  Fielding CR  Isbell JL  Birgenheier LP  Rygel MC 《Science (New York, N.Y.)》2007,315(5808):87-91

The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.  相似文献   

In vivo activation of the p53 pathway by small-molecule antagonists of MDM2     

Vassilev LT  Vu BT  Graves B  Carvajal D  Podlaski F  Filipovic Z  Kong N  Kammlott U  Lukacs C  Klein C  Fotouhi N  Liu EA 《Science (New York, N.Y.)》2004,303(5659):844-848

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Population genetics. Estonia prepares for national DNA database     

Frank L 《Science (New York, N.Y.)》2000,290(5489):31

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Chloride methylation by plant pectin: an efficient environmentally significant process     

Hamilton JT  McRoberts WC  Keppler F  Kalin RM  Harper DB 《Science (New York, N.Y.)》2003,301(5630):206-209

Atmospheric chloromethane (CH3Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH3Cl is produced in many terrestrial environments by a common mechanism. Abiotic conversion of chloride to CH3Cl occurs readily in plant material, with the widespread plant component pectin acting as a methyl donor. Significant CH3Cl emissions from senescent and dead leaves were observed at ambient temperatures; those emissions rose dramatically when temperatures increased. This ubiquitous process acting in terrestrial ecosystems and during biomass burning could contribute the bulk of atmospheric CH3Cl.  相似文献   

ASTRONOMY. Waves in the Sun's core     

Hill F 《Science (New York, N.Y.)》2007,316(5831):1573-1574

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