《自然》（20190613出版）一周論文導讀

翻譯 | 唐一塵

Nature, 13 June 2019, Volume 570 Issue 7760

《自然》2019年6月13日，第7760期570卷

古生物Paleontology

Early fungi from the Proterozoic era in Arctic Canada

加拿大北極元古代的早期真菌

作者：Corentin C.Loron、Camille Fran?ois、Emmanuelle J. Javaux，etal

鏈接：

https://www.nature.com/articles/s41586-019-1217-0

摘要：

真菌是現代生態系統的關鍵組成成分，並且與陸地上最早的生命跡象有關。儘管如此，真菌的化石記錄一直以來只能追溯至約4億年前的中古生代。

本研究報告了有機質壁微體化石Ourasphaira giraldae樣本，它們保存在加拿大西北地區草灣構造的河口頁岩內。

研究人員在樣本的細胞壁內鑒定出了有隔菌絲和幾丁質，確定O. giraldae的結構為典型的真菌結構。這代表了地質記錄中最早的幾丁質——形成真菌細胞壁的纖維性物質。

以上發現也將後鞭毛生物（真核生物的一個主要類群，包括動物和真菌）的起源時間大大向前推進至中元古宙時期。

Abstract

Fungi are crucial components of modern ecosystems. They may have had an important role in the colonization of land by eukaryotes, and inthe appearance and success of land plants and metazoans. Nevertheless, fossils that can unambiguously be identified as fungi are absent from the fossil record until the middle of the Palaeozoic era. Here we show, using morphological, ultrastructural and spectroscopic analyses, that multicellular organic-walled microfossils preserved in shale of the Grassy Bay Formation (Shaler Supergroup, Arctic Canada), which dates to approximately 1,010–890 million years ago, have a fungal affinity. These microfossils are more than half a billion years older than previously reported unambiguous occurrences of fungi, a date whichis consistent with data from molecular clocks for the emergence of this clade. In extending the fossil record of the fungi, this finding also pushes back the minimum date for the appearance of eukaryotic crown group Opisthokonta, which comprises metazoans, fungi and their protist relatives.

Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America

古愛斯基摩人的遺傳祖先和楚科奇人與北美人的關係

作者：Pavel Flegontov、N. Ezgi Alt?n???k、Stephan Schiffels，etal

鏈接：

https://www.nature.com/articles/s41586-019-1251-y

摘要：

約5000年前，古愛斯基摩人成為了美洲北極廣闊地區的首批定居者，1000年前左右，現代因紐特人和尤皮克人的祖先陸續抵達，並從很大程度上取代了古愛斯基摩人。

不過，古愛斯基摩人和美洲土著人、因紐特人、尤皮克人和阿留申人這些群體之間的親緣關係一直未得到確定。

本論文分析了來自美洲北極和西伯利亞的48例古代個體的基因組數據，這些地區包括楚科奇、東西伯利亞、阿留申群島、阿拉斯加和加拿大北極。

此外，研究人員還報道了現代阿拉斯加伊努皮亞特人以及西西伯利亞人群的數據。

分析顯示，北美人群歷史主要來自於古愛斯基摩人與首批美洲人之間的基因流，這也是以愛斯基摩—阿留申語系和納-德內語為母語人群的起源。

Abstract

Much of the American Arctic was first settled 5,000 years ago, by groups of people known as Palaeo-Eskimos. They were subsequently joined and largely displaced around 1,000 years ago by ancestors of the present-day Inuit and Yup』ik. The genetic relationship between Palaeo-Eskimos and Native American, Inuit, Yup』ik and Aleut populations remains uncertain. Here we present genomic data for 48 ancient individuals from Chukotka, East Siberia, the Aleutian Islands, Alaska, and the Canadian Arctic. We co-analyse these data with data from present-day Alaskan I?upiat and West Siberian populations and published genomes. Using methods based on rare-allele and haplotype sharing, as well as established techniques, we show that Palaeo-Eskimo-related ancestry is ubiquitous among people who speak Na-Dene and Eskimo–Aleut languages. We develop a comprehensive model for the Holocene peopling events of Chukotka and North America, and show that Na-Dene-speaking peoples, people of the Aleutian Islands, and Yup』ik and Inuit across the Arctic region all share ancestry from a single Palaeo-Eskimo-related Siberian source.

The population history of northeastern Siberia since the Pleistocene

西伯利亞東北部自更新世以來的人口歷史

作者：Martin Sikora、Vladimir V. Pitulko、Eske Willerslev，et al

鏈接：

https://www.nature.com/articles/s41586-019-1279-z

摘要：

西伯利亞東北部已經有4萬多年的人類居住歷史，但人們對其深厚的人口歷史仍知之甚少。

本研究報道了西伯利亞東北部（今俄羅斯遠東地區）的34例古基因組，這些基因組來自距今31000年至600年前。雖然人類在這一地區居住已有4萬多年，但其深度人群歷史卻鮮為人知。

研究人員記錄下了這一時期的複雜人群動態，包括至少3次主要遷移事件：此前不為人知的舊石器時代古代北西伯利亞人群的首次抵達，這一人群也是早期西歐亞狩獵採集者的遠親；東亞人群的抵達以及隨後誕生的古代古西伯利亞人和美洲土著人；名為新西伯利亞人的東亞人群的全新世遷移，許多當代西伯利亞人都是他們的後裔。

Abstract

Northeastern Siberia has been inhabited by humans for more than 40,000 years but its deep population history remains poorly understood. Here we investigate the late Pleistocene population history of northeastern Siberia through analyses of 34 newly recovered ancient genomes that date to between 31,000 and 600 years ago. We document complex population dynamics during this period, including at least three major migration events: an initial peopling by a previously unknown Palaeolithic population of 『Ancient North Siberians』 who are distantly related to early West Eurasian hunter-gatherers; the arrival of East Asian-related peoples, which gave rise to『Ancient Palaeo-Siberians』 who are closely related to contemporary communities from far-northeastern Siberia (such as the Koryaks), as well as Native Americans; and a Holocene migration of other East Asian-related peoples, who we name 『Neo-Siberians』, and from whom many contemporary Siberians are descended. Each of these population expansions largely replaced the earlier inhabitants, and ultimately generated the mosaic genetic make-up of contemporary peoples who inhabit a vast area across northern Eurasia and the Americas.

健康Health

Mapping HIV prevalence in sub-Saharan Africa between 2000 and 2017

繪製2000年至2017年撒哈拉以南非洲地區艾滋病病毒流行情況地圖

作者：Laura Dwyer-Lindgren、Michael A.Cork、Simon I. Hay，et al

鏈接：

https://www.nature.com/articles/s41586-019-1200-9

摘要：

儘管治療方法有了進步，但是艾滋病仍是撒哈拉以南非洲的主要疾病負擔來源，而且是該區域最常見的死因。擁有更加詳細的關於艾滋病病毒（HIV）流行率差異的信息，或有助於預防和治療HIV感染。

本研究全面分析了2000年至2017年47個撒哈拉以南非洲國家的HIV流行率。所用數據都來自調查和保健診所，這些數據提供了HIV在15~49歲成人群體中的流行率估算值。

研究人員比較了每個國家各行政區域之間的流行率以及5x5千米網格區域之間的流行率情況。

結果顯示國家之間和各國國內不同區域都存在明顯的差異——HIV整體流行率較低的國家，其國內也有局部區域呈現出較高的HIV流行率。在其中15個國家，國家層面的HIV流行率在2000年至2017年之間上升了，不過在局部區域這種趨勢存在差異。

該研究或有助於採用精準干預手段，控制撒哈拉以南非洲的HIV感染。

Abstract

HIV/AIDS is a leading cause of disease burden in sub-Saharan Africa. Existing evidence has demonstrated that there is substantial local variation in the prevalence of HIV; however, subnational variation has not been investigated at a high spatial resolution across the continent. Here we explore within-country variation at a 5 × 5-km resolution in sub-Saharan Africa by estimating the prevalence of HIV among adults (aged 15–49 years) and the corresponding number of people living with HIV from 2000 to 2017. Our analysis reveals substantial within-country variation in the prevalence of HIV through out sub-Saharan Africa and local differences in both the direction and rate of change in HIV prevalence between 2000 and 2017, highlighting the degree to which important local differences are masked when examining trends at the country level. These fine-scale estimates of HIV prevalence across space and time provide an important tool for precisely targeting the interventions that are necessary to bringing HIV infections under control in sub-Saharan Africa.

Metabolic control of BRISC–SHMT2 assembly regulates immune signalling

BRISC–SHMT2組裝的代謝調控控制免疫信號

作者：Miriam Walden、Lei Tian、Elton Zeqiraj，etal

鏈接：

https://www.nature.com/articles/s41586-019-1232-1

摘要：

免疫細胞及其被稱為細胞因子的信號化合物的過度生產，會引發過度炎症，導致大量組織損傷。一種參與修復受損DNA的酶也存在於一個叫做BRISC的單獨複合物中，用來調節免疫信號。

研究人員利用低溫電子顯微鏡計算出了分子複合物的結構。他們的發現揭示了一種有趣的分子機制，將BRISC與一種參與代謝的酶——絲氨酸羥甲基轉移酶2 (SHMT2)聯繫起來。

在被激活後，SHMT2引導對基本身體功能至關重要的反應，如蛋白質和DNA的構建塊。

研究小組發現SHMT2還通過與BRISC複合物的相互作用誘導免疫細胞釋放細胞因子。破壞BRISC-SHMT2結合區域的突變干擾了炎症的侵襲，這或有助於開發狼瘡藥物新靶點。

Abstract

Serine hydroxymethyltransferase 2 (SHMT2) regulates one-carbon transfer reactions that are essential for amino acid and nucleotide metabolism, and uses pyridoxal-5′-phosphate (PLP) as a cofactor. Apo SHMT2 exists as a dimer with unknown functions, whereas PLP binding stabilizes the active tetrameric state. SHMT2 also promotes inflammatory cytokine signallingby interacting with the deubiquitylating BRCC36 isopeptidase complex (BRISC), although it is unclear whether this function relates to metabolism. Here we present the cryo-electron microscopy structure of the human BRISC–SHMT2 complexat a resolution of 3.8 ?. BRISC is a U-shaped dimer of four subunits, and SHMT2 sterically blocks the BRCC36 active site and inhibits deubiquitylase activity. Only the inactive SHMT2 dimer—and not the active PLP-bound tetramer—binds and inhibits BRISC. Mutations in BRISC that disrupt SHMT2 binding impair type I interferon signalling in response to inflammatory stimuli. Intracellular levels of PLP regulate the interaction between BRISC and SHMT2, as well as inflammatory cytokine responses. These data reveal amechanism in which metabolites regulate deubiquitylase activity and inflammatory signalling.

物理Physics

Elastic colloidal monopoles and reconfigurable self-assembly in liquid crystals

液晶中的彈性膠體磁單極子及可重構自組裝

作者：Ye Yuan、Qingkun Liu、Bohdan Senyuk、Ivan I. Smalyukh

鏈接：

https://www.nature.com/articles/s41586-019-1247-7

摘要：

類磁單極子靜電相互作用在生物學和凝聚態物質中是普遍存在的，但它們往往被反離子屏蔽，不能從吸引態轉變為排斥態。

在膠體學中，主要目標是開發膠體粒子，模擬和超越原子和分子組裝的多樣性和長度尺度，帶靜電粒子不能改變其表面電荷的符號，也不能從單極轉變為高階多極。

本研究用非結構光演示了這些膠體粒子從單極到四極的重排，它類似於原子在基態和各種激發態之間的驅動。

研究人員證明了彈性磁單極子的符號是可以被轉換的，並且與靜電學中不同，同性電荷的磁單極子相互吸引，而異性電荷的磁單極子相互排斥。研究還證明了這些膠體粒子的非平衡動態組裝。

Abstract

Monopole-like electrostatic interactions are ubiquitous in biology and condensed matter, but they are often screened by counter-ions and cannot be switched from attractive to repulsive. In colloidal science, where the main goal is to develop colloidal particles that mimic and exceed the diversity and length scales of atomic and molecular assembly, electrostatically charged particles cannot change the sign of their surface charge or transform from monopoles to higher-order multipoles. In liquid-crystal colloids, elastic interactions between particlesarise to minimize the free energy associated with elastic distortions in the long-range alignment of rod-like molecules around the particles. In dipolar,quadrupolar and hexadecapolar nematic colloids, the symmetries of such elastic distortions mimic both electrostatic multipoles and the outermost occupied electron shells of atoms. Electric and magnetic switching, spontaneous transformations and optical control of elastic multipoles, as well as their interactions with topological defects and surface boundary conditions, have been demonstrated in such colloids. However, it has long been understood that elastic monopoles should relax to uniform or higher-order multipole statesbecause of the elastic torques that they induce. Here we develop nematiccolloids with strong elastic monopole moments and with elastic torques balanced by the optical torques induced by ambient light. We demonstrate the monopole-to-quadrupole reconfiguration of these colloidal particles by unstructured light, which resembles the driving of atoms between the groundstate and various excited states. We show that the sign of the elasticmonopoles can be switched, and that like-charged monopoles attract whereas oppositely charged ones repel, unlike in electrostatics. We also demonstratethe out-of-equilibrium dynamic assembly of these colloidal particles. This diverse and surprising behaviour is explained using a model that considers the balance of the optical and elastic torques that are responsible for the excited-state elastic monopoles and may lead to light-powered active-matter systems and self-assembled nanomachines.

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