世界生命科学前沿动态周报（十二）

【点评】
点评：通过不断提供LIF生长因子和持续表达5个重新编程因子，可以控制人体诱导多能干细（iPSC）保持在更原始的多能干细胞状态，该技术最大的用处就是便于建立iPSC细胞系，但是还不能改变基因重新编程的iPSC没有临床应用价值的情形。

【原文摘录】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. 控制流感病毒复制的“开关”
【摘要】科技日报 2010-6-7 10:31:18
　　据报道，美国科学家首次发现流感病毒的复制存在一个控制“开关”——小病毒核糖核酸（svRNA），并有望据此研发出能够治疗所有类型流感的药物。甲型流感病毒包含8个单体RNA片段，每个片段都有两个任务：通过转录过程制造蛋白；通过复制过程制造出新的病毒片段。因为每个单体必须执行两个功能，病毒必须让某一个过程优先完成，先转录然后再开始复制。通过使用超高通量测序技术，纽约西奈山医学院的研究人员首次找到了甲型流感病毒中的一个svRNA，并确定它就是控制病毒从转录过渡到复制的“开关”。超高通量测序技术是对传统测序手段的一次革命性改变，它一次就可对几十万到几百万条DNA分子进行序列测定，使得对一个物种的转录组和基因组进行细致全貌的分析成为可能，所以又被称为深度测序。该研究的领导者之一、西奈山医学院微生物学家本杰明·腾奥弗表示，这项研究的意义十分重大。在流感病毒中，svRNA始终如一地位于病毒RNA片段之间，并且在每种流感病毒中都出现。如果我们能够阻止svRNA的活性，就能控制病毒不要转向复制过程，从而阻止其扩散。另外的一个好处是，如果病毒只能转录，那它就只能不断产生蛋白，反而最终会强化抗体的反应能力。
　　腾奥弗指出，理论上讲，通过抑制svRNA就可以阻止病毒片段的复制，但现在的问题是，我们还不了解svRNA的“工作细节”，我们也希望能够找到一种方法，让基于RNA的对抗剂进入人体中，用来抑制svRNA的功能，让病毒不转向复制过程。不过，这个问题可能还需要几年才能解决。由于乙型流感和丙型流感病毒的复制策略和甲型流感病毒的一样，这个发现也就意味着我们将最终能够研制出一种能够治疗所有流感病毒的药物。虽然甲型H1N1流感的阴影正在消散，但我们从来没有忘记，仅季节性流感每年就要夺去全世界25万人的生命。一说到流感，你可能马上想起疫苗。然而，流感病毒的进化和变异非常快，疫苗也必须随之不断更新，而且还不见得有效。所以，科学家们一方面试图培育出万能流感疫苗，另一方面也从治疗的角度努力开发通用抗流感药物，从而对流感病毒形成前后夹击之势。腾奥弗和他的团队今天带给我们的正是后者的希望。
【点评】
点评：从理论上发现了可以研制出对抗所有流感病毒感染的药物的策略。

【原文摘录】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细胞基因改造制造癌细胞杀手
　　

【摘要】 《科学》期刊新发表的一项研究发现通过敲除T细胞必须基因Bcl11b能够获得类似NK细胞的ITNK细胞，在体外实验和老鼠动物模型上这种细胞能够消灭癌细胞和预防肿瘤的形成和转移。而且可以维持存活至少3个月，没有发现携带该细胞的老鼠出现异常。【点评】
点评：该发现为癌症的免疫疗法提供了新的线索。

【原文摘录】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. 红酒和绿茶中多酚类化合物抗癌的机理
　　

【摘要】SphK1/S1P信号通路是与许多癌症的进展及治疗抵抗相关的，最新的研究证明绿茶里的儿茶素（ＥＧＣＧ），红酒中的白藜芦醇（Ｒｅｓｖｅｒａｔｒｏｌ），或者各自提取的混合多酚类都能在体内外实验中抑制前列腺癌细胞的生长，是通过抑制SphK1/S1P信号通路实现的，第一次从分子生物学解读解释了此类食物中多酚化合物在癌症预防和治疗中的分子靶标。
【点评】
点评：该研究提供了确定的证据，有助于理解绿茶和红酒的抗癌保健功能，也为抗癌药物的研究提供了新靶点。

【原文摘录】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干扰素激活休眠的造血干细胞

【摘要】 全身感染会迅速消耗体内的淋巴细胞和中性粒细胞，造血系统的祖细胞会增产免疫细胞来恢复体内平衡。最新的动物实验研究了造血干细胞在这一过程中的行为，发现在鸡结核杆菌慢性感染大的老鼠中造血干细胞长期的增多的增殖反应必须有γ干扰素的参与，这一结论也在γ干扰素缺失的老鼠身上得到验证。
【点评】
点评：该研究有助于更好的理解一些慢性感染病患的免疫体系重建要素，更深入理解造血系统如何恢复免疫细胞的数量。

【原文摘录】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. 肿瘤抑制因子ｐ５３在生殖细胞减数分裂中也有生理作用

【摘要】 肿瘤抑制因子ｐ５３生物学作用不仅体现在抑制肿瘤发生，最近的动物实验表明生殖细胞的减数分裂过程，特别是拓扑异构酶Ｓｐｏ１１催化的ＤＮＡ双链解开激活了ｐ５３的功能，并一直存在于无法进行减数分裂ＤＮＡ修复的细胞中。这一发现确证了ｐ５３在减数分裂中有生理作用，也提示了ｐ５３的抑制肿瘤发生的作用可能是在执行更原始的与基因重组相关的功能时分派的。
【点评】
点评：ｐ５３抑制肿瘤生成的作用看来有可能是其最本源的功能的附带功能。

【原文摘录】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