目次

Editorial

環境保護活動家たちと手を結ぶべきか手を切るべきか

To build bridges, or to burn them p.481

Environmentalists who have grown impatient with science and technology need not be dismissed as beyond the reach of reason.

doi: 10.1038/443481a

News

Youthful duo snags a swift Nobel for RNA control of genes p.488

Award comes just eight years after publication.

doi: 10.1038/443488a

Cosmic ripples net physics prize p.489

Vision of early Universe makes its mark.

doi: 10.1038/443489a

News & Views

ナノ技術:SQUIDを小型化する

Nanotechnology: Downsizing SQUIDs p.517

doi: 10.1038/443517a

News and Views Feature

遺伝学:進化の推進力となるジャンクDNA

Genetics: Junk DNA as an evolutionary force p.521

Transposable elements were long dismissed as useless, but they are emerging as major players in evolution. Their interactions with the genome and the environment affect how genes are translated into physical traits.

doi: 10.1038/443521a

Articles

遺伝:酵母の倍数性に関するゲノム規模の遺伝的解析

Genome-wide genetic analysis of polyploidy in yeast p.541

Polyploidy, increased sets of chromosomes, occurs during development, cellular stress, disease and evolution. Despite its prevalence, little is known about the physiological alterations that accompany polyploidy. We previously described ‘ploidy-specific lethality’, where a gene deletion that is not lethal in haploid or diploid budding yeast causes lethality in triploids or tetraploids. Here we report a genome-wide screen to identify ploidy-specific lethal functions. Only 39 out of 3,740 mutations screened exhibited ploidy-specific lethality. Almost all of these mutations affect genomic stability by impairing homologous recombination, sister chromatid cohesion, or mitotic spindle function. We uncovered defects in wild-type tetraploids predicted by the screen, and identified mechanisms by which tetraploidization affects genomic stability. We show that tetraploids have a high incidence of syntelic/monopolar kinetochore attachments to the spindle pole. We suggest that this defect can be explained by mismatches in the ability to scale the size of the spindle pole body, spindle and kinetochores. Thus, geometric constraints may have profound effects on genome stability; the phenomenon described here may be relevant in a variety of biological contexts, including disease states such as cancer.

doi: 10.1038/nature05178

生化学:AB5サチラーゼ細胞毒素は小胞体シャペロンBiPを不活性化する

AB5 subtilase cytotoxin inactivates the endoplasmic reticulum chaperone BiP p.548

AB5 toxins are produced by pathogenic bacteria and consist of enzymatic A subunits that corrupt essential eukaryotic cell functions, and pentameric B subunits that mediate uptake into the target cell. AB5 toxins include the Shiga, cholera and pertussis toxins and a recently discovered fourth family, subtilase cytotoxin, which is produced by certain Shiga toxigenic strains of Escherichia coli. Here we show that the extreme cytotoxicity of this toxin for eukaryotic cells is due to a specific single-site cleavage of the essential endoplasmic reticulum chaperone BiP/GRP78. The A subunit is a subtilase-like serine protease; structural studies revealed an unusually deep active-site cleft, which accounts for its exquisite substrate specificity. A single amino-acid substitution in the BiP target site prevented cleavage, and co-expression of this resistant protein protected transfected cells against the toxin. BiP is a master regulator of endoplasmic reticulum function, and its cleavage by subtilase cytotoxin represents a previously unknown trigger for cell death.

doi: 10.1038/nature05124

Letters

量子情報科学:光と物質との間の量子テレポーテーション

Quantum teleportation between light and matter p.557

doi: 10.1038/nature05136

海洋:ダンスガード- オシュガー・サイクルを通じた 亜熱帯北大西洋における急速な塩分振動

Rapid subtropical North Atlantic salinity oscillations across Dansgaard–Oeschger cycles p.561

doi: 10.1038/nature05121

地球:中央海嶺の玄武岩供給源における沈み込みによって富化したマントルの存在を示唆するリチウム同位体の証拠

Lithium isotope evidence for subduction-enriched mantle in the source of mid-ocean-ridge basalts p.565

doi: 10.1038/nature05144

遺伝:Deinococcus radioduransにおける分断された染色体の再構築

Reassembly of shattered chromosomes in Deinococcus radiodurans p.569

doi: 10.1038/nature05160

遺伝:多発性硬化症に関連するMHCの共通ハプロタイプの機能的なエピスタシス

Functional epistasis on a common MHC haplotype associated with multiple sclerosis p.574

doi: 10.1038/nature05133

細胞:細胞内のマラリア原虫による、ナトリウムに依存した無機リン酸の取り込み

Sodium-dependent uptake of inorganic phosphate by the intracellular malaria parasite p.582

doi: 10.1038/nature05149

細胞:哺乳類ミトコンドリアのポルフィリン輸送体の同定

Identification of a mammalian mitochondrial porphyrin transporter p.586

doi: 10.1038/nature05125

生化学:DDB1-CUL4Aユビキチンリガーゼ複合体の分子構造と会合機構

Molecular architecture and assembly of the DDB1–CUL4A ubiquitin ligase machinery p.590

doi: 10.1038/nature05175

進化:細胞周期に応じた転写調節と翻訳後調節の共進化

Co-evolution of transcriptional and post-translational cell-cycle regulation p.594

doi: 10.1038/nature05186

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