世界生命科學(xué)前沿動(dòng)態(tài)周報(bào)（十二）

【點(diǎn)評(píng)】
點(diǎn)評(píng)：通過不斷提供LIF生長(zhǎng)因子和持續(xù)表達(dá)5個(gè)重新編程因子，可以控制人體誘導(dǎo)多能干細(xì)（iPSC）保持在更原始的多能干細(xì)胞狀態(tài)，該技術(shù)最大的用處就是便于建立iPSC細(xì)胞系，但是還不能改變基因重新編程的iPSC沒有臨床應(yīng)用價(jià)值的情形。

【原文摘錄】Cell Stem Cell, Volume 6, Issue 6, 535-546, 4 June 2010
A Murine ESC-like State Facilitates Transgenesis and Homologous Recombination in Human Pluripotent Stem Cells
Christa Buecker, Hsu-Hsin Chen, Jose Maria Polo, Laurence Daheron, Lei Bu, Tahsin Stefan Barakat, Patricia Okwieka, Andrew Porter, Joost Gribnau, Konrad Hochedlinger and Niels Geijsen
Murine pluripotent stem cells can exist in two functionally distinct states, LIF-dependent embryonic stem cells (ESCs) and bFGF-dependent epiblast stem cells (EpiSCs). However, human pluripotent cells so far seemed to assume only an epiblast-like state. Here we demonstrate that human iPSC reprogramming in the presence of LIF yields human stem cells that display morphological, molecular, and functional properties of murine ESCs. We termed these hLR5 iPSCs because they require the expression of five ectopic reprogramming factors, Oct4, Sox2, Klf4, cMyc, and Nanog, to maintain this more naive state. The cells are metastable and upon ectopic factor withdrawal they revert to standard human iPSCs. Finally, we demonstrate that the hLR5 state facilitates gene targeting, and as such provides a powerful tool for the generation of recombinant human pluripotent stem cell lines.

2. 控制流感病毒復(fù)制的“開關(guān)”
【摘要】科技日?qǐng)?bào) 2010-6-7 10:31:18
　　據(jù)報(bào)道，美國(guó)科學(xué)家首次發(fā)現(xiàn)流感病毒的復(fù)制存在一個(gè)控制“開關(guān)”——小病毒核糖核酸（svRNA），并有望據(jù)此研發(fā)出能夠治療所有類型流感的藥物。甲型流感病毒包含8個(gè)單體RNA片段，每個(gè)片段都有兩個(gè)任務(wù)：通過轉(zhuǎn)錄過程制造蛋白；通過復(fù)制過程制造出新的病毒片段。因?yàn)槊總€(gè)單體必須執(zhí)行兩個(gè)功能，病毒必須讓某一個(gè)過程優(yōu)先完成，先轉(zhuǎn)錄然后再開始復(fù)制。通過使用超高通量測(cè)序技術(shù)，紐約西奈山醫(yī)學(xué)院的研究人員首次找到了甲型流感病毒中的一個(gè)svRNA，并確定它就是控制病毒從轉(zhuǎn)錄過渡到復(fù)制的“開關(guān)”。超高通量測(cè)序技術(shù)是對(duì)傳統(tǒng)測(cè)序手段的一次革命性改變，它一次就可對(duì)幾十萬到幾百萬條DNA分子進(jìn)行序列測(cè)定，使得對(duì)一個(gè)物種的轉(zhuǎn)錄組和基因組進(jìn)行細(xì)致全貌的分析成為可能，所以又被稱為深度測(cè)序。該研究的領(lǐng)導(dǎo)者之一、西奈山醫(yī)學(xué)院微生物學(xué)家本杰明·騰奧弗表示，這項(xiàng)研究的意義十分重大。在流感病毒中，svRNA始終如一地位于病毒RNA片段之間，并且在每種流感病毒中都出現(xiàn)。如果我們能夠阻止svRNA的活性，就能控制病毒不要轉(zhuǎn)向復(fù)制過程，從而阻止其擴(kuò)散。另外的一個(gè)好處是，如果病毒只能轉(zhuǎn)錄，那它就只能不斷產(chǎn)生蛋白，反而最終會(huì)強(qiáng)化抗體的反應(yīng)能力。
　　騰奧弗指出，理論上講，通過抑制svRNA就可以阻止病毒片段的復(fù)制，但現(xiàn)在的問題是，我們還不了解svRNA的“工作細(xì)節(jié)”，我們也希望能夠找到一種方法，讓基于RNA的對(duì)抗劑進(jìn)入人體中，用來抑制svRNA的功能，讓病毒不轉(zhuǎn)向復(fù)制過程。不過，這個(gè)問題可能還需要幾年才能解決。由于乙型流感和丙型流感病毒的復(fù)制策略和甲型流感病毒的一樣，這個(gè)發(fā)現(xiàn)也就意味著我們將最終能夠研制出一種能夠治療所有流感病毒的藥物。雖然甲型H1N1流感的陰影正在消散，但我們從來沒有忘記，僅季節(jié)性流感每年就要奪去全世界25萬人的生命。一說到流感，你可能馬上想起疫苗。然而，流感病毒的進(jìn)化和變異非?？欤呙缫脖仨氹S之不斷更新，而且還不見得有效。所以，科學(xué)家們一方面試圖培育出萬能流感疫苗，另一方面也從治療的角度努力開發(fā)通用抗流感藥物，從而對(duì)流感病毒形成前后夾擊之勢(shì)。騰奧弗和他的團(tuán)隊(duì)今天帶給我們的正是后者的希望。
【點(diǎn)評(píng)】
點(diǎn)評(píng)：從理論上發(fā)現(xiàn)了可以研制出對(duì)抗所有流感病毒感染的藥物的策略。

【原文摘錄】Published online before print June 1, 2010, doi: 10.1073/pnas.1001984107
Influenza A virus-generated small RNAs regulate the switch from transcription to replication
Jasmine T. Perez, Andrew Varble, Ravi Sachidanandam, Ivan Zlatev, Muthiah Manoharan,
Adolfo García-Sastre, and Benjamin R. tenOever

The discovery of regulatory small RNAs continues to reshape paradigms in both molecular biology and virology. Here we describe examples of influenza A virus-derived small viral RNAs (svRNAs). svRNAs are 22–27 nt in length and correspond to the 5′ end of each of the viral genomic RNA (vRNA) segments. Expression of svRNA correlates with the accumulation of vRNA and a bias in RNA-dependent RNA polymerase (RdRp) activity from transcription toward genome replication. Synthesis of svRNA requires the RdRp, nucleoprotein and the nuclear export protein NS2. In addition, svRNA is detectable during replication of various influenza A virus subtypes across multiple host species and associates physically with the RdRp. We demonstrate that depletion of svRNA has a minimal impact on mRNA and complementary vRNA (cRNA) but results in a dramatic loss of vRNA in a segment-specific manner. We propose that svRNA triggers the viral switch from transcription to replication through interactions with the viral polymerase machinery. Taken together, the discovery of svRNA redefines the mechanistic switch of influenza virus transcription/replication and provides a potential target for broad-range, anti-influenza virus-based therapeutics.
3. T細(xì)胞基因改造制造癌細(xì)胞殺手
　　

【摘要】 《科學(xué)》期刊新發(fā)表的一項(xiàng)研究發(fā)現(xiàn)通過敲除T細(xì)胞必須基因Bcl11b能夠獲得類似NK細(xì)胞的ITNK細(xì)胞，在體外實(shí)驗(yàn)和老鼠動(dòng)物模型上這種細(xì)胞能夠消滅癌細(xì)胞和預(yù)防腫瘤的形成和轉(zhuǎn)移。而且可以維持存活至少3個(gè)月，沒有發(fā)現(xiàn)攜帶該細(xì)胞的老鼠出現(xiàn)異常?！军c(diǎn)評(píng)】
點(diǎn)評(píng)：該發(fā)現(xiàn)為癌癥的免疫療法提供了新的線索。

【原文摘錄】Published Online June 10, 2010  Science DOI: 10.1126/science.1188063
Reprogramming of T cells to Natural Killer-like cells upon Bcl11b deletion.
Peng Li, Shannon Burke, Juexuan Wang, Xiongfeng Chen, Mariaestela Ortiz, Song-Choon Lee, Dong Lu, Lia Campos, David Goulding, Bee Ling Ng, Gordon Dougan, Brian Huntly, Bertie Gottgens, Nancy A. Jenkins, Neal G. Copeland, Francesco Colucci, and Pentao Liu.

T cells develop in the thymus and are critical for adaptive immunity. Natural killer (NK) lymphocytes constitute an essential component of the innate immune system in tumor surveillance and defense against microbes and viruses. Here, we show that the transcription factor Bcl11b was expressed in all T cell compartments and was indispensable for T-lineage development. When Bcl11b was deleted, T cells from all developmental stages acquired NK cell properties and concomitantly lost or decreased T cell–associated gene expression. These induced T-to-natural-killer (ITNK) cells, which were morphologically and genetically similar to conventional NK cells, killed tumor cells in vitro and effectively prevented tumor metastasis in vivo. Therefore, ITNKs may represent a new cell source for cell-based therapies.
4. 紅酒和綠茶中多酚類化合物抗癌的機(jī)理
　　

【摘要】SphK1/S1P信號(hào)通路是與許多癌癥的進(jìn)展及治療抵抗相關(guān)的，最新的研究證明綠茶里的兒茶素（ＥＧＣＧ），紅酒中的白藜蘆醇（Ｒｅｓｖｅｒａｔｒｏｌ），或者各自提取的混合多酚類都能在體內(nèi)外實(shí)驗(yàn)中抑制前列腺癌細(xì)胞的生長(zhǎng)，是通過抑制SphK1/S1P信號(hào)通路實(shí)現(xiàn)的，第一次從分子生物學(xué)解讀解釋了此類食物中多酚化合物在癌癥預(yù)防和治療中的分子靶標(biāo)。
【點(diǎn)評(píng)】
點(diǎn)評(píng)：該研究提供了確定的證據(jù)，有助于理解綠茶和紅酒的抗癌保健功能，也為抗癌藥物的研究提供了新靶點(diǎn)。

【原文摘錄】The FASEB Journal, 2010; DOI: 10.1096/fj.10-160838
The sphingosine kinase-1 survival pathway is a molecular target for the tumor-suppressive tea and wine polyphenols in prostate cancer
Leyre Brizuela, Audrey Dayon, Nicolas Doumerc, Isabelle Ader, Muriel Golzio, Jean-Claude Izard, Yukihiko Hara, Bernard Malavaud, and Olivier Cuvillier

The sphingosine kinase-1/sphingosine 1-phosphate (SphK1/S1P) pathway has been associated with cancer promotion and progression and resistance to treatments in a number of cancers, including prostate adenocarcinoma. Here we provide the first evidence that dietary agents, namely, epigallocatechin gallate (EGCg, IC5075 μM), resveratrol (IC5040 μM), or a mixture of polyphenols from green tea [polyphenon E (PPE), IC5070 μM] or grapevine extract (vineatrol, IC5030 μM), impede prostate cancer cell growth in vitro and in vivo by inhibiting the SphK1/S1P pathway. We establish that SphK1 is a downstream effector of the ERK/phospholipase D (PLD) pathway, which is inhibited by green tea and wine polyphenols. Enforced expression of SphK1 impaired the ability of green tea and wine polyphenols, as well as pharmacological inhibitors of PLD and ERK activities, to induce apoptosis in PC-3 and C4-2B cells. The therapeutic efficacy of these polyphenols on tumor growth and the SphK1/S1P pathway were confirmed in animals using a heterotopic PC-3 tumor in place model. PC-3/SphK1 cells implanted in animals developed larger tumors and resistance to treatment with polyphenols. Furthermore, using an orthotopic PC-3/GFP model, the chemopreventive effect of an EGCg or PPE diet was associated with SphK1 inhibition, a decrease in primary tumor volume, and occurrence and number of metastases. These results provide the first demonstration that the prosurvival, antiapoptotic SphK1/S1P pathway represents a target of dietary green tea and wine polyphenols in cancer.
5. 慢性感染使γ干擾素激活休眠的造血干細(xì)胞

【摘要】 全身感染會(huì)迅速消耗體內(nèi)的淋巴細(xì)胞和中性粒細(xì)胞，造血系統(tǒng)的祖細(xì)胞會(huì)增產(chǎn)免疫細(xì)胞來恢復(fù)體內(nèi)平衡。最新的動(dòng)物實(shí)驗(yàn)研究了造血干細(xì)胞在這一過程中的行為，發(fā)現(xiàn)在雞結(jié)核桿菌慢性感染大的老鼠中造血干細(xì)胞長(zhǎng)期的增多的增殖反應(yīng)必須有γ干擾素的參與，這一結(jié)論也在γ干擾素缺失的老鼠身上得到驗(yàn)證。
【點(diǎn)評(píng)】
點(diǎn)評(píng)：該研究有助于更好的理解一些慢性感染病患的免疫體系重建要素，更深入理解造血系統(tǒng)如何恢復(fù)免疫細(xì)胞的數(shù)量。

【原文摘錄】Nature, 2010; 465 (7299): 793 DOI: 10.1038/nature09135
Quiescent haematopoietic stem cells are activated by IFN-γ in response to chronic infection
Megan T. Baldridge, Katherine Y. King, Nathan C. Boles, David C. Weksberg, Margaret A. Goodell

Lymphocytes and neutrophils are rapidly depleted by systemic infection. Progenitor cells of the haematopoietic system, such as common myeloid progenitors and common lymphoid progenitors, increase the production of immune cells to restore and maintain homeostasis during chronic infection, but the contribution of haematopoietic stem cells (HSCs) to this process is largely unknown. Here we show, using an in vivo mouse model of Mycobacterium avium infection, that an increased proportion of long-term repopulating HSCs proliferate during M. avium infection, and that this response requires interferon-γ (IFN-γ) but not interferon-α (IFN-α) signalling. Thus, the haematopoietic response to chronic bacterial infection involves the activation not only of intermediate blood progenitors but of long-term repopulating HSCs as well. IFN-γ is sufficient to promote long-term repopulating HSC proliferation in vivo; furthermore, HSCs from IFN-γ-deficient mice have a lower proliferative rate, indicating that baseline IFN-γ tone regulates HSC activity. These findings implicate IFN-γ both as a regulator of HSCs during homeostasis and under conditions of infectious stress. Our studies contribute to a deeper understanding of haematological responses in patients with chronic infections such as HIV/AIDS or tuberculosis.
6. 腫瘤抑制因子ｐ５３在生殖細(xì)胞減數(shù)分裂中也有生理作用

【摘要】 腫瘤抑制因子ｐ５３生物學(xué)作用不僅體現(xiàn)在抑制腫瘤發(fā)生，最近的動(dòng)物實(shí)驗(yàn)表明生殖細(xì)胞的減數(shù)分裂過程，特別是拓?fù)洚悩?gòu)酶Ｓｐｏ１１催化的ＤＮＡ雙鏈解開激活了ｐ５３的功能，并一直存在于無法進(jìn)行減數(shù)分裂ＤＮＡ修復(fù)的細(xì)胞中。這一發(fā)現(xiàn)確證了ｐ５３在減數(shù)分裂中有生理作用，也提示了ｐ５３的抑制腫瘤發(fā)生的作用可能是在執(zhí)行更原始的與基因重組相關(guān)的功能時(shí)分派的。
【點(diǎn)評(píng)】
點(diǎn)評(píng)：ｐ５３抑制腫瘤生成的作用看來有可能是其最本源的功能的附帶功能。

【原文摘錄】Science, 2010; 328 (5983): 1278 DOI: 10.1126/science.1185640
Meiotic Recombination Provokes Functional Activation of the p53 Regulatory Network
Wan-Jin Lu, Joseph Chapo, Ignasi Roig, John M. Abrams