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排序方式: 共有1815条查询结果,搜索用时 15 毫秒
121.
Culliton BJ 《Science (New York, N.Y.)》1975,187(4173):237-239+
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Role of histone H3 lysine 27 methylation in X inactivation 总被引:1,自引:0,他引:1
Plath K Fang J Mlynarczyk-Evans SK Cao R Worringer KA Wang H de la Cruz CC Otte AP Panning B Zhang Y 《Science (New York, N.Y.)》2003,300(5616):131-135
The Polycomb group (PcG) protein Eed is implicated in regulation of imprinted X-chromosome inactivation in extraembryonic cells but not of random X inactivation in embryonic cells. The Drosophila homolog of the Eed-Ezh2 PcG protein complex achieves gene silencing through methylation of histone H3 on lysine 27 (H3-K27), which suggests a role for H3-K27 methylation in imprinted X inactivation. Here we demonstrate that transient recruitment of the Eed-Ezh2 complex to the inactive X chromosome (Xi) occurs during initiation of X inactivation in both extraembryonic and embryonic cells and is accompanied by H3-K27 methylation. Recruitment of the complex and methylation on the Xi depend on Xist RNA but are independent of its silencing function. Together, our results suggest a role for Eed-Ezh2-mediated H3-K27 methylation during initiation of both imprinted and random X inactivation and demonstrate that H3-K27 methylation is not sufficient for silencing of the Xi. 相似文献
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Casassus B 《Science (New York, N.Y.)》2004,303(5663):1446
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Uhlmann WR Bennett R Botkin JR Botstein D Boughman JA Chakravarti A Clayton EW Kahn J Koenig B Murray TH Olson MV Rowley J Terry S Valle D 《Science (New York, N.Y.)》2003,299(5612):1515; author reply 1515
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Pang PT Teng HK Zaitsev E Woo NT Sakata K Zhen S Teng KK Yung WH Hempstead BL Lu B 《Science (New York, N.Y.)》2004,306(5695):487-491
Long-term memory is thought to be mediated by protein synthesis-dependent, late-phase long-term potentiation (L-LTP). Two secretory proteins, tissue plasminogen activator (tPA) and brain-derived neurotrophic factor (BDNF), have been implicated in this process, but their relationship is unclear. Here we report that tPA, by activating the extracellular protease plasmin, converts the precursor proBDNF to the mature BDNF (mBDNF), and that such conversion is critical for L-LTP expression in mouse hippocampus. Moreover, application of mBDNF is sufficient to rescue L-LTP when protein synthesis is inhibited, which suggests that mBDNF is a key protein synthesis product for L-LTP expression. 相似文献
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Hirjibehedin CF Lin CY Otte AF Ternes M Lutz CP Jones BA Heinrich AJ 《Science (New York, N.Y.)》2007,317(5842):1199-1203
Magnetic anisotropy allows magnets to maintain their direction of magnetization over time. Using a scanning tunneling microscope to observe spin excitations, we determined the orientation and strength of the anisotropies of individual iron and manganese atoms on a thin layer of copper nitride. The relative intensities of the inelastic tunneling processes are consistent with dipolar interactions, as seen for inelastic neutron scattering. First-principles calculations indicate that the magnetic atoms become incorporated into a polar covalent surface molecular network in the copper nitride. These structures, which provide atom-by-atom accessibility via local probes, have the potential for engineering anisotropies large enough to produce stable magnetization at low temperatures for a single atomic spin. 相似文献