排序方式: 共有51条查询结果,搜索用时 218 毫秒
1.
2.
Kondo Y Shen L Cheng AS Ahmed S Boumber Y Charo C Yamochi T Urano T Furukawa K Kwabi-Addo B Gold DL Sekido Y Huang TH Issa JP 《Nature genetics》2008,40(6):741-750
Epigenetic silencing in cancer cells is mediated by at least two distinct histone modifications, polycomb-based histone H3 lysine 27 trimethylation (H3K27triM) and H3K9 dimethylation. The relationship between DNA hypermethylation and these histone modifications is not completely understood. Using chromatin immunoprecipitation microarrays (ChIP-chip) in prostate cancer cells compared to normal prostate, we found that up to 5% of promoters (16% CpG islands and 84% non-CpG islands) were enriched with H3K27triM. These genes were silenced specifically in prostate cancer, and those CpG islands affected showed low levels of DNA methylation. Downregulation of the EZH2 histone methyltransferase restored expression of the H3K27triM target genes alone or in synergy with histone deacetylase inhibition, without affecting promoter DNA methylation, and with no effect on the expression of genes silenced by DNA hypermethylation. These data establish EZH2-mediated H3K27triM as a mechanism of tumor-suppressor gene silencing in cancer that is potentially independent of promoter DNA methylation. 相似文献
3.
Nishimoto S Kawane K Watanabe-Fukunaga R Fukuyama H Ohsawa Y Uchiyama Y Hashida N Ohguro N Tano Y Morimoto T Fukuda Y Nagata S 《Nature》2003,424(6952):1071-1074
The eye lens is composed of fibre cells, which develop from the epithelial cells on the anterior surface of the lens. Differentiation into a lens fibre cell is accompanied by changes in cell shape, the expression of crystallins and the degradation of cellular organelles. The loss of organelles is believed to ensure the transparency of the lens, but the molecular mechanism behind this process is not known. Here we show that DLAD ('DNase II-like acid DNase', also called DNase IIbeta) is expressed in human and murine lens cells, and that mice deficient in the DLAD gene are incapable of degrading DNA during lens cell differentiation--the undigested DNA accumulates in the fibre cells. The DLAD-/- mice develop cataracts of the nucleus lentis, and their response to light on electroretinograms is severely reduced. These results indicate that DLAD is responsible for the degradation of nuclear DNA during lens cell differentiation, and that if DNA is left undigested in the lens, it causes cataracts of the nucleus lentis, blocking the light path. 相似文献
4.
Cell stimulation causes diacylglycerol kinase (DGK) to convert the second messenger diacylglycerol into phosphatidate, thus initiating the resynthesis of phosphatidylinositols and attenuating protein kinase C activity. Of the DGK isoforms so far reported, only porcine DGK from lymphocytes has been characterized in detail. Here we report the isolation and sequencing of complementary DNA clones that together cover the entire region encoding porcine DGK (relative molecular mass 80,000 (80K)). The deduced primary structure of this DGK contains the putative ATP-binding sites, two cysteine-rich zinc finger-like sequences similar to those found in protein kinase C, and two E-F hand motifs, typical of Ca2(+)-binding proteins like calmodulin. Indeed, we find that the activity of this DGK isoform is enhanced by micromolar concentrations of Ca2+ in the presence of deoxycholate or sphingosine. These properties of 80K DGK indicate that its action is probably linked with both of the second messengers diacylglycerol and inositol 1,4,5-trisphosphate. 相似文献
5.
Enhanced atmospheric loss on protoplanets at the giant impact phase in the presence of oceans 总被引:1,自引:0,他引:1
The atmospheric compositions of Venus and Earth differ significantly, with the venusian atmosphere containing about 50 times as much 36Ar as the atmosphere on Earth. The different effects of the solar wind on planet-forming materials for Earth and Venus have been proposed to account for some of this difference in atmospheric composition, but the cause of the compositional difference has not yet been fully resolved. Here we propose that the absence or presence of an ocean at the surface of a protoplanet during the giant impact phase could have determined its subsequent atmospheric amount and composition. Using numerical simulations, we demonstrate that the presence of an ocean significantly enhances the loss of atmosphere during a giant impact owing to two effects: evaporation of the ocean, and lower shock impedance of the ocean compared to the ground. Protoplanets near Earth's orbit are expected to have had oceans, whereas those near Venus' orbit are not, and we therefore suggest that remnants of the noble-gas rich proto-atmosphere survived on Venus, but not on Earth. Our proposed mechanism explains differences in the atmospheric contents of argon, krypton and xenon on Venus and Earth, but most of the neon must have escaped from both planets' atmospheres later to yield the observed ratio of neon to argon. 相似文献
6.
Genome sequencing and analysis of Aspergillus oryzae 总被引:4,自引:0,他引:4
Machida M Asai K Sano M Tanaka T Kumagai T Terai G Kusumoto K Arima T Akita O Kashiwagi Y Abe K Gomi K Horiuchi H Kitamoto K Kobayashi T Takeuchi M Denning DW Galagan JE Nierman WC Yu J Archer DB Bennett JW Bhatnagar D Cleveland TE Fedorova ND Gotoh O Horikawa H Hosoyama A Ichinomiya M Igarashi R Iwashita K Juvvadi PR Kato M Kato Y Kin T Kokubun A Maeda H Maeyama N Maruyama J Nagasaki H Nakajima T Oda K Okada K Paulsen I Sakamoto K Sawano T Takahashi M Takase K Terabayashi Y Wortman JR Yamada O 《Nature》2005,438(7071):1157-1161
The genome of Aspergillus oryzae, a fungus important for the production of traditional fermented foods and beverages in Japan, has been sequenced. The ability to secrete large amounts of proteins and the development of a transformation system have facilitated the use of A. oryzae in modern biotechnology. Although both A. oryzae and Aspergillus flavus belong to the section Flavi of the subgenus Circumdati of Aspergillus, A. oryzae, unlike A. flavus, does not produce aflatoxin, and its long history of use in the food industry has proved its safety. Here we show that the 37-megabase (Mb) genome of A. oryzae contains 12,074 genes and is expanded by 7-9 Mb in comparison with the genomes of Aspergillus nidulans and Aspergillus fumigatus. Comparison of the three aspergilli species revealed the presence of syntenic blocks and A. oryzae-specific blocks (lacking synteny with A. nidulans and A. fumigatus) in a mosaic manner throughout the genome of A. oryzae. The blocks of A. oryzae-specific sequence are enriched for genes involved in metabolism, particularly those for the synthesis of secondary metabolites. Specific expansion of genes for secretory hydrolytic enzymes, amino acid metabolism and amino acid/sugar uptake transporters supports the idea that A. oryzae is an ideal microorganism for fermentation. 相似文献
7.
Yutaka Baba 《系统科学与系统工程学报(英文版)》2010,19(4):496-503
We study an M/PH/1 queue with phase type working vacation and vacation interruption where the vacation time follows a phase
type distribution. The server serves the customers at a lower rate in a vacation period. The server comes back to the regular
busy period at a service completion without completing the vacation. Such policy is called vacation interruption. In terms
of quasi birth and death process and matrix-geometric solution method, we obtain the stationary queue length distribution.
Moreover we obtain the conditional stochastic decomposition structures of queue length and waiting time when the service time
distribution in the regular busy period is exponential. 相似文献
8.
The amphioxus genome and the evolution of the chordate karyotype 总被引:2,自引:0,他引:2
Putnam NH Butts T Ferrier DE Furlong RF Hellsten U Kawashima T Robinson-Rechavi M Shoguchi E Terry A Yu JK Benito-Gutiérrez EL Dubchak I Garcia-Fernàndez J Gibson-Brown JJ Grigoriev IV Horton AC de Jong PJ Jurka J Kapitonov VV Kohara Y Kuroki Y Lindquist E Lucas S Osoegawa K Pennacchio LA Salamov AA Satou Y Sauka-Spengler T Schmutz J Shin-I T Toyoda A Bronner-Fraser M Fujiyama A Holland LZ Holland PW Satoh N Rokhsar DS 《Nature》2008,453(7198):1064-1071
9.
This paper describes the latest version of the Chinese-Japanese-English handheld speech-tospeech translation system developed by NICT/ATR, which is now ready to be deployed for travelers. With the entire speech-to-speech translation function being implemented into one terminal, it realizes real-time, location-free speech-to-speech translation. A new noise-suppression technique notably improves the speech recognition performance. Corpus-based approaches of speech recognition, machine translation, and speech synthesis enable coverage of a wide variety of topics and portability to other languages. Test results show that the character accuracy of speech recognition is 82%-94% for Chinese speech, with a bilingual evaluation understudy score of machine translation is 0.55-0.74 for Chinese-Japanese and Chinese-English 相似文献
10.
与中国在纪年采用西历的同时很多传统节日仍然延续农历行事的状况不同,日本在推行西方历法之后出现了传统节日适应于西历的现象,如新年元旦虽以西历日期为准其内涵却是农历新年的习俗。但因为国家意识、人口流动、媒体宣传以及商业资本等原因,这种被认为是"传统"的元旦文化发生了很大的变化,现代版的元旦文化其实只是各类文化元素的集合体所形成的一种抽象的形象化而已,已经不存在具有整体面貌的元旦文化了。但民众在其中选择自己喜好的文化元素,即使发生某种变化也在体验实际而具体的节日文化所带来的快乐,其变化所反映的勃勃生机以及创造性正是现代日本都市社会的节日文化之传承本质和继承方式。 相似文献