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2007年7月12日Nature中文摘要
 BIOX.CN  来源：生命经纬    2007年07月12日
封面故事：拓扑异构酶和DNA超级螺旋
Antitumour drugs impede DNA uncoiling by topoisomerase I
拓扑异构酶（Topoisomerases）的作用是使超级螺旋松弛。所谓超级螺旋是DNA
中张力积聚的一种形式。拓扑异构酶抑制成分是重要抗肿瘤药物，被认为通过稳
定拓扑异构酶与DNA之间所形成的一种共价复合物来发挥作用，后者又为DNA复制
机制设置了一个障碍。科学家对以拓扑异构酶为作用目标的药物的药效的起源仍
然不是很了解，但现在对Topotecan（一种主要用来治疗卵巢癌和小细胞肺癌的
药物）和一种拓扑异构酶IB-DNA复合物之间的相互作用所做的一项单分子研究，
显示了这一过程中更为详细的 内容。本期封面图片所示为由于该药物（图中用
红色表示）的作用而造成的正向DNA超级螺旋的积累。DNA的这种超级缠绕会妨碍
一种DNA聚合酶的前行，并且在阻止或破坏复制叉（replication fork）、从而
导致细胞死亡过程中也可能扮演一个角色。（Letter p. 213）封面图片：U
Delft/Tremani


整个基因组范围内特定组织的果蝇RNAi库（Release those inhibitions）
A genome-wide transgenic RNAi library for conditional gene
inactivation in Drosophila
利用一套完整的基因组序列数据（在本例中为Drosophila Release 4.3），从所
预测出的蛋白编码基因（达到了88%的覆盖率）来生成干涉RNA转基因，这样你就
获得了一个非常强大的工具。来自维也纳分子生物技术研究所的一个小组，已经
生成并确认了一个整个基因组范围内的、针对具体组织的果蝇RNAi库，这个数据
库将有助于对功能的丧失进行快速的基因筛选，使得科学家基本上有可能在生物
体的生命过程中的任何阶段在任何一种组织中或细胞中来研究基因功能。这个数
据库将为很多领域的研究工作铺平道路，包括行为研究、睡眠研究、学习研究、
病理研究和衰老研究，这些领域以前是无法用成功应用于发育生物学的那种系统
性基因分析方法来进行研究的。（Article p. 151; News）


RNA聚合酶的结构和功能（RNA polymerase up close）
Structural basis for transcription elongation by bacterial RNA
polymerase / Structural basis for substrate loading in bacterial RNA
polymerase
本期两篇互补的论文是关于细菌RNA聚合酶的结构和功能的。在第一篇论文中，
研究人员将这种酶与DNA模板和RNA产物结合在一起，以对转录伸长复合物进行仔
细观测。该结构显示了DNA到RNA的转录过程的详细情况，这个转录过程对于所有
活细胞都是至关重要的。在第二篇论文中，RNA聚合酶伸长复合物是与各种不同
的基质类比物和一种抗生素结合在一起的，显示了基质加载和抗生素抑制的机
制。对人类和细菌 RNA聚合酶的结构进行对比，将有助于进行药物设计：RNA聚
合酶是包括利福霉素（rifamycin）及其衍生物在内的抗生素的一个作用目标。
（Articles p. 157, 163; News & Views）


“热木星”大气层中含有水蒸气的可信证据（A hint of water）
Water vapour in the atmosphere of a transiting extrasolar planet
天文学家已经探测到了超过200颗绕太阳以外的恒星运转的行星。它们当中很多
都是“热木星”，即绕其恒星近距离运转的巨大的太阳系外行星。但尽管理论工
作者预测这种行星的大气中含有丰富的水，但这方面的证据迄今为止却都是模棱
两可的。现在，Tinetti等人已经获得了可信的证据，它表明，热木星至少在其
大气层中含有水蒸气。编号为HD189733b的行星是当它在其母恒星前面经过时在
红外波段被观测到的。在不同波长所观测到的半径的明显变化，可以用水蒸气的
吸收来做最好的解释。（Letter p. 169; News & Views）


彗星73P不同碎片组成非常相似（Comet 73P in pieces）
Compositional homogeneity in the fragmented comet 73P/Schwassmann–
Wachmann 3
彗星73P/Schwassmann-Wachmann 3 (comet 73P)2006年的造访使其非常靠近地
球。十年之前，该彗星分裂成了至少5个碎片，而到2006年，有超过60个碎片绕
太阳运转。该彗星的分裂将以前深埋在其原始核中的新鲜物质暴露了出来。这为
天文学家提供了与美国国家航空航天局（NASA）的“深层撞击”探测器所创造的
条件相同的理想的自然条件，深入彗星的深度甚至超过该探测器撞击彗星Tempel
1时所达到的深度。对comet 73P的碎片B和碎片C所做的观测表明，它们在组成上
非常相似。这与不同彗星之间在组成上的明显差别性成对比，并且也与以前认为
短周期彗星的组成将随深度发生很大变化的假设相矛盾。（Letter p. 172;
News & Views）


海洋沉积物能从固氮变为释放氮（From sink to source）
Reversal of the net dinitrogen gas flux in coastal marine sediments
到达沿海水域的大多数氮被海洋沉积物中的反硝化作用所清除。然而，固氮作用
在亚潮异养海洋系统中被认为是一个可以忽略的过程。现在，Fulweiler等人发
现，海洋沉积物能从一个净氮汇转变成一个净氮源。研究人员将模仿沿海海洋环
境的实验结果与关于年平均叶绿素产量的一个历史数据集结合起来，发现由气候
诱导的初级生产的下降导致向海床中沉降的有机质的数量下降，也导致所观测到
的沉积物净氮通量的逆转。因此，一些河口地区可能不再提供它们曾经所提供的
有用的氮留持及清除服务。这一变化有可能将人类活动所造成的氮加载效应从近
岸沿海地区延伸到开阔海洋中。（Letter p. 180）


物种灭绝是否会影响生态系统功能（Biodiversity: The more the merrier）
Biodiversity and ecosystem multifunctionality
物种灭绝是否改变物种群落的生产力和生态系统的功能的问题，多年时间都是一
个有争议的问题。一系列综合分析达成了某种共识：物种损失并不会损害生态系
统功能，但这要取决于损失的是哪种物种：很多物种似乎在功能上是冗余的。在
过去，研究工作主要集中在各个不同的生态系统过程上，尽管事实上多数生态系
统要提供几种生态系统服务。Andy Hector 和Robert Bagchi对来自草地生物多
样性实验的已经发表的数据进行了分析，以了解生物多样性与多种生态系统功能
之间的关系。他们发现，不同物种经常影响不同生态系统功能，所以只关注一个
生态系统过程的研究工作可能会忽略全局情况。因此，多功能生态系统保证其存
活所需要的生物多样性可能要比以前的研究工作所认为的更大。（Letter p.
188）


一种新的多功能胚胎干细胞（A new type of stem cell）
Derivation of pluripotent epiblast stem cells from mammalian embryos /
New cell lines from mouse epiblast share defining features with human
embryonic stem cells
人类胚胎干细胞在治疗方面有潜在的重要性，因为它们有多种功能，如果给予适
当条件的话，它们能够分化成几乎任何类型的细胞。影响关于它们的研究工作的
进展的一个障碍是，人类与小鼠胚胎干细胞之间存在令人困惑的差别。现在，独
立工作的两个小组生成了一种新的多功能胚胎干细胞。这些外胚层干细胞
（EpiSCs）是在小鼠胚胎在子宫壁上着床之后从它们当中提取出来的，与“经典
的”小鼠胚胎干细胞明显不同，而与人类胚胎干细胞的关键特征却很相似。
EpiSCs的发现应能为加快人类胚胎干细胞在研究（最终也许还包括治疗）中的应
用提供一个重要的实验模型。（Letters pp. 191, 196）


薄荷醇受体TRPM8在感知冷热中所起作用（A chilly receptor）
The menthol receptor TRPM8 is the principal detector of environmental
cold
各种不同的通道、输送因子和细胞类型都被认为与对寒冷刺激的感知有关，而关
于这些因素中的每一个在感知无害之冷与有害之冷中所起的作用，研究人员已经
争论了一些时间。薄荷醇受体TRPM8（也被称为CMR1） 很可能是一种冷传导因
子，但其在生理上的重要性却受到了质疑。对剔出TRPM8的小鼠的体觉
（somato-sensory）功能所做的一项研究澄清了有关疑问。没有这种受体的小鼠
在所有层次上（在细胞层次上、在完好的神经纤维上和在完整动物（行为）试验
中）感知寒冷的能力都存在缺陷。TRPM8显然是周围寒冷感觉的主要贡献因素，
缺少这一通道的动物在温度降到低于10 °C之前不能区分热冷表面。（Letter
p. 204; News & Views）


第二种“低硅”基因Lsi2被发现（Two-way street for silicon）
An efflux transporter of silicon in rice
硅在植物生长中起一种有益的作用：它能增强植物抗病虫害和倒伏的能力，提供
植物在一个群落中的光截获能力，减少蒸发作用所造成的损失。水稻是一种典型
的硅积累型植物，能够在茎杆中增加硅的含量，这是因为其根能够从土壤中吸收
硅。现在，由于第二种“低硅”基因Lsi2（该基因在细胞膜内壁上编码一种硅外
流输送因子）的发现，使水稻能够做到这一点的复杂系统已被更为充分地定性。
Lsi1基因已知编码内流输送因子，后者存在于细胞膜的外壁上。（Letter p.
209）


----------------------
NEWS AND VIEWS
----------------------
Photonics: Light in chains pp141 - 142
Diffraction places a fundamental limit on the smallest scales at which
light can be controlled. A nanoscale silver array not only circumvents
the barrier, but steers different-coloured light to different places.
Niek F. van Hulst
doi:10.1038/448141a
http://www.nature.com/nature/journal/v448/n7150/full/448141a.html

Gene transcription: Extending the message pp142 - 143
During transcription, RNA polymerase catalyses the addition of
nucleotides to the growing RNA chain. High-resolution structural
snapshots indicate that the polymerase first identifies its substrate,
and then incorporates it.
Patrick Cramer
doi:10.1038/448142a
http://www.nature.com/nature/journal/v448/n7150/full/448142a.html

Extrasolar planets: Water on distant worlds pp143 - 145
Is the presence of water a feature common to all gas-giant planets?
The first convincing detection of water vapour in the atmosphere of
such a planet from outside our Solar System indicates that the answer
is yes.
Heather A. Knutson
doi:10.1038/448143a
http://www.nature.com/nature/journal/v448/n7150/full/448143a.html

Plant ecology: Family roots pp145 - 147
Experiments in which related and unrelated plants were grown together
reveal the ability of roots to recognize their kin. The ecological and
evolutionary implications are tantalizing topics for future studies.
Ragan M. Callaway and Bruce E. Mahall
doi:10.1038/448145a
http://www.nature.com/nature/journal/v448/n7150/full/448145a.html

50 & 100 Years Ago p146
doi:10.1038/448146a
http://www.nature.com/nature/journal/v448/n7150/full/448146a.html

Neurophysiology: Channelling cold reception pp147 - 148
Perception of cold and hot is one of life's essentials. Three research
teams find that, when a temperature-sensing receptor is deleted in
mice, the animals lose their response to a range of cold temperatures.
Bernd Nilius and Thomas Voets
doi:10.1038/448147a
http://www.nature.com/nature/journal/v448/n7150/full/448147a.html

Toxicology: Danger in the diet p148
Tim Lincoln
doi:10.1038/448148a
http://www.nature.com/nature/journal/v448/n7150/full/448148a.html

Obituary: Pierre-Gilles de Gennes (1932-2007) p149
Pioneer of soft-matter physics.
Francoise Brochard-Wyart
doi:10.1038/448149a
http://www.nature.com/nature/journal/v448/n7150/full/448149a.html

----------------------
ARTICLES
----------------------
A genome-wide transgenic RNAi library for conditional gene
inactivation in Drosophila pp151 - 156
A library of transgenic flies expressing RNAi in a conditional manner,
for virtually every gene in the Drosophila melanogaster genome, has
been generated. This resource will allow the community to test the
function of every gene, in any cell type, at any development stage, or
in response to various types of experimental stimulations.
Georg Dietzl et al.
doi:10.1038/nature05954
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05954.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05954.html

Structural basis for transcription elongation by bacterial RNA
polymerase pp157 - 162
Crystal structure of bacterial RNA polymerase bound to the DNA
template and RNA product, revealing a detailed view of the
transcription elongation complex.
Dmitry G. Vassylyev et al.
doi:10.1038/nature05932
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05932.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05932.html

Structural basis for substrate loading in bacterial RNA
polymerase pp163 - 168
Crystal structures of bacterial RNA polymerase elongation complexes
bound to NTP substrate analogues with an antibiotic, revealing the
mechanism of substrate loading and antibiotic inhibition.
Dmitry G. Vassylyev et al.
doi:10.1038/nature05931
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05931.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05931.html

----------------------
LETTERS
----------------------
Water vapour in the atmosphere of a transiting extrasolar
planet pp169 - 171
A report of recent observations of the close-in extrasolar giant
planet (hot Jupiter) HD 189733b taken during the transit, where the
planet passed in front of its parent star. Absorption by water vapour
is the most likely cause of the wavelength-dependent variations in the
effective radius of the planet.
Giovanna Tinetti et al.
doi:10.1038/nature06002
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature06002.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature06002.html

Compositional homogeneity in the fragmented comet
73P/Schwassmann-Wachmann 3 pp172 - 175
A report of the chemical composition of two distinct fragments of
comet 73P/Schwassmann-Wachmann 3. The fragments are similar in
composition, in contrast to the chemical diversity of comets and
contrary to the expectation that short-period comets should show
strong compositional variation with depth.
N. Dello Russo et al.
doi:10.1038/nature05908
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05908.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05908.html

High-resolution spectroscopy of two-dimensional electron
systems pp176 - 179
A powerful new spectroscopic technique (high-resolution time-domain
capacitance spectroscopy) for detailed exploration of the energy
structure of two-dimensional electron systems (2DES) gives a
quantitative and precise view of electron-electron interactions in a
2DES, and reveals several phenomena at energies that cannot be reached
with other techniques.
O. E. Dial, R. C. Ashoori, L. N. Pfeiffer and K. W. West
doi:10.1038/nature05982
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05982.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05982.html

Reversal of the net dinitrogen gas flux in coastal marine
sediments pp180 - 182
Marine sediments can switch from being a net sink to a net source of
nitrogen. Mesocosm and core incubation experiments, together with a
historic data set of mean annual chlorophyll production, suggest that
a climate-induced decrease in primary production has led to a decrease
in organic matter deposition to the benthos and the observed reversal
of the net sediment nitrogen flux.
R. W. Fulweiler, S. W. Nixon, B. A. Buckley and S. L. Granger
doi:10.1038/nature05963
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05963.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05963.html

Spreading rate dependence of gravity anomalies along oceanic transform
faults pp183 - 187
Gravity and bathymetry data from transform fault systems associated
with mid-ocean ridges that are spreading at different rates indicates
that crustal thickening may occur under transform faults associated
with intermediate- and fast-spreading ridges. If confirmed, this
observation would require a change in our understanding of how magma
accretion occurs along rapidly spreading mid-ocean ridges.
Patricia M. Gregg, Jian Lin, Mark D. Behn and Laurent G. J. Montesi
doi:10.1038/nature05962
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05962.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05962.html

Biodiversity and ecosystem multifunctionality pp188 - 190
An analysis of published data from grassland biodiversity experiments
looks at the relationship between biodiversity and multiple ecological
processes (ecosystem multifunctionality). Different species often
influence different ecosystem functions, suggesting that studies
considering single ecosystem services in isolation may severely
underestimate the levels of biodiversity required for fully
functioning ecosystems.
Andy Hector and Robert Bagchi
doi:10.1038/nature05947
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05947.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05947.html

Derivation of pluripotent epiblast stem cells from mammalian
embryos pp191 - 195
A study revealing that pluripotent stem cells (EpiSCs) can be derived
from the late epiblast layer of post-implantation mouse and rat
embryos. To achieve this, a chemically defined, activin-containing
culture medium known to be sufficient for long-term maintenance of
human embryonic stem cells is used. These findings will help to
understand the biological provenance of human embryonic stem cells.
I. Gabrielle M. Brons et al.
doi:10.1038/nature05950
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05950.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05950.html

New cell lines from mouse epiblast share defining features with human
embryonic stem cells pp196 - 199
Mouse and human embryonic stem (ES) cells use different signalling
pathways to maintain their pluripotent status. Now, a new kind of
pluripotent ES cell is described. This cell type is derived from mouse
embryos after they implant in the wall of the uterus, and shares many
defining features with human ES cells, including signalling responses
that control differentiation to somatic fates.
Paul J. Tesar et al.
doi:10.1038/nature05972
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05972.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05972.html

An intracellular P2X receptor required for osmoregulation in
Dictyostelium discoideum pp200 - 203
Membrane ion channels of the P2X class, which are gated by
extracellular ATP, have been thought to be an exclusivity of
multicellular organisms. Now, a functional P2X receptor in the social
amoeba Dictyostelium discoideum has been found. It helps D. discoideum
to adapt its cell volume to conditions of salinity. This discovery
suggests vastly expanded modes of action for this important class of
membrane receptors.
Samuel J. Fountain et al.
doi:10.1038/nature05926
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05926.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05926.html

The menthol receptor TRPM8 is the principal detector of environmental
cold pp204 - 208
The identity of the transduction molecules underlying cold sensation
has long been a mystery in sensory physiology. Now, using a
combination of electrophysiological recording, calcium imaging and
behavioural analysis, TRPM8 is shown to have a major role in normal
cold transduction in mice.
Diana M. Bautista et al.
doi:10.1038/nature05910
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05910.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05910.html

An efflux transporter of silicon in rice pp209 - 212
Jian Feng Ma et al.
doi:10.1038/nature05964
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05964.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05964.html

Antitumour drugs impede DNA uncoiling by topoisomerase I pp213
- 217
A report on single topoisomerase molecules in action, showing that
topoisomerase inhibitors don't just stabilize an intermediate but
actually affect the ability of topoisomerase to relax DNA
supercoiling, suggesting a new mechanism by which these drugs cause
cytotoxicity.
Daniel A. Koster et al.
doi:10.1038/nature05938
Abstract:
http://www.nature.com/nature/journal/v448/n7150/abs/nature05938.html
Article:
http://www.nature.com/nature/journal/v448/n7150/full/nature05938.html
 
    
 


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