Activation of the cellular DNA damage response in the absence of DNA lesions   总被引：1，自引：0，他引：1  

Soutoglou E  Misteli T 《Science (New York, N.Y.)》2008,320(5882):1507-1510

The cellular DNA damage response (DDR) is initiated by the rapid recruitment of repair factors to the site of DNA damage to form a multiprotein repair complex. How the repair complex senses damaged DNA and then activates the DDR is not well understood. We show that prolonged binding of DNA repair factors to chromatin can elicit the DDR in an ATM (ataxia telangiectasia mutated)- and DNAPK (DNA-dependent protein kinase)-dependent manner in the absence of DNA damage. Targeting of single repair factors to chromatin revealed a hierarchy of protein interactions within the repair complex and suggests amplification of the damage signal. We conclude that activation of the DDR does not require DNA damage and stable association of repair factors with chromatin is likely a critical step in triggering, amplifying, and maintaining the DDR signal.  相似文献   

Regular Production of Transgenic Wheat Mediated by Agrobacterium tumefaciens   总被引：4，自引：1，他引：4  

YE Xing-guo  Shirley Sato  XU Hui-jun  DU Li-Pu  Tom Clemente 《中国农业科学(英文版)》2002,1(3):239-244

Wheat is the number one crop both in acreage and total yield in the world. Therefore, it is very important to improve wheat by gene engineering techniques even though it belongs to the plants insensitive to gene transformation, especially to Agrobacterium-mediated transformation. Wheat immature embryos of 1.0-1.5mm in size, C58c1 of Agrobacterium strain harboring pPTN249, pPTN270, pPTN254, and pSIS-GFP respectively (all the vectors contain the aphA selectable gene driven by enhanced 35S promoter and a target gene controlled by ubi promoter or E35S promoter), AB medium for Agrobacterium activate culture, WCC medium for co-culture, were used in this study. The embryos with 4 days of pre-culture were transferred onto selection medium with 10mg/L geneticin, 50mg/L ticarcillin, 50mg/L vancomycin, and 50mg/L cefotaxine after 30 minutes of infection and 2 days of co-cultivation with Agrobacterium. Followed callus production,shoot regeneration on selection medium, 114 resistant plantlets were obtained from 10 transformation experiments of four genotypes. By nptⅡ ELISA (nptⅡ enzyme assay), PCR, Southern blot and leaf bleach,29 positive plants were identified from two genotypes of Bobwhite and Yanglmai 10, with an average transformation efficiency of 0.82 %. The result tested by Southern blot also showed that the transgenic plants with single- copy integration of target gene took 65.52% among total positive plants. The ELISA value of transgenic plant was also related to the copies of alien DNA integrating into wheat chromosomes, the transgenic plants with single copy integration giving higher ELISA value than the ones with 2 or 3 copies integration.  相似文献   

Crystal structure of the long-chain fatty acid transporter FadL     

van den Berg B  Black PN  Clemons WM  Rapoport TA 《Science (New York, N.Y.)》2004,304(5676):1506-1509

The mechanisms by which hydrophobic molecules, such as long-chain fatty acids, enter cells are poorly understood. In Gram-negative bacteria, the lipopolysaccharide layer in the outer membrane is an efficient barrier for fatty acids and aromatic hydrocarbons destined for biodegradation. We report crystal structures of the long-chain fatty acid transporter FadL from Escherichia coli at 2.6 and 2.8 angstrom resolution. FadL forms a 14-stranded beta barrel that is occluded by a central hatch domain. The structures suggest that hydrophobic compounds bind to multiple sites in FadL and use a transport mechanism that involves spontaneous conformational changes in the hatch.  相似文献   

Genome-sequencing anniversary. Genomics and clinical relevance     

Hudson T 《Science (New York, N.Y.)》2011,331(6017):547

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210th meeting of the American Astronomical Society. Black holes: galactic homebodies?     

Siegfried T 《Science (New York, N.Y.)》2007,316(5830):1420

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Membrane proteins of the endoplasmic reticulum induce high-curvature tubules     

Hu J  Shibata Y  Voss C  Shemesh T  Li Z  Coughlin M  Kozlov MM  Rapoport TA  Prinz WA 《Science (New York, N.Y.)》2008,319(5867):1247-1250

The tubular structure of the endoplasmic reticulum (ER) appears to be generated by integral membrane proteins, the reticulons and a protein family consisting of DP1 in mammals and Yop1p in yeast. Here, individual members of these families were found to be sufficient to generate membrane tubules. When we purified yeast Yop1p and incorporated it into proteoliposomes, narrow tubules (approximately 15 to 17 nanometers in diameter) were generated. Tubule formation occurred with different lipids; required essentially only the central portion of the protein, including its two long hydrophobic segments; and was prevented by mutations that affected tubule formation in vivo. Tubules were also formed by reconstituted purified yeast Rtn1p. Tubules made in vitro were narrower than normal ER tubules, due to a higher concentration of tubule-inducing proteins. The shape and oligomerization of the "morphogenic" proteins could explain the formation of the tubular ER.  相似文献   

Molecular biology. Breaking the silence     

Owen-Hughes T  Bruno M 《Science (New York, N.Y.)》2004,303(5656):324-325

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Molecular mechanisms for the functionality of lubricant additives     

Mosey NJ  Müser MH  Woo TK 《Science (New York, N.Y.)》2005,307(5715):1612-1615

Wear limits the life-span of many mechanical devices with moving parts. To reduce wear, lubricants are frequently enriched with additives, such as zinc phosphates, that form protective films on rubbing surfaces. Using first-principles molecular dynamics simulations of films derived from commercial additives, we unraveled the molecular origin of how antiwear films can form, function, and dissipate energy. These effects originate from pressure-induced changes in the coordination number of atoms acting as cross-linking agents to form chemically connected networks. The proposed mechanism explains a diverse body of experiments and promises to prove useful in the rational design of antiwear additives that operate on a wider range of surface materials, with reduced environmental side effects.  相似文献   

American Physical Society meeting. Gravity probe researchers report 'glimpses' of long-awaited payoff     

Siegfried T 《Science (New York, N.Y.)》2007,316(5824):538-539

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Monte Verde: seaweed, food, medicine, and the peopling of South America     

Dillehay TD  Ramírez C  Pino M  Collins MB  Rossen J  Pino-Navarro JD 《Science (New York, N.Y.)》2008,320(5877):784-786

The identification of human artifacts at the early archaeological site of Monte Verde in southern Chile has raised questions of when and how people reached the tip of South America without leaving much other evidence in the New World. Remains of nine species of marine algae were recovered from hearths and other features at Monte Verde II, an upper occupational layer, and were directly dated between 14,220 and 13,980 calendar years before the present ( approximately 12,310 and 12,290 carbon-14 years ago). These findings support the archaeological interpretation of the site and indicate that the site's inhabitants used seaweed from distant beaches and estuarine environments for food and medicine. These data are consistent with the ideas that an early settlement of South America was along the Pacific coast and that seaweeds were important to the diet and health of early humans in the Americas.  相似文献