Science：“垃圾DNA”在基因组中的重要功能
生物谷：科学家直到最近才开始思考“垃圾DNA”（junk DNA）可能由于某个重要原因而存在于基因组中。垃圾DNA是人类基因组中96%不编译任何蛋白质的DNA，它们过去被认为是无用的。现在，来自加州大学San Diego分校（UCSD）医学院的科学家们发现了它们的一项重要功能。
基因是基因组中4%的编译蛋白DNA－生命的构件（building blocks）。由UCSD医学教授Michael G. Rosenfeld领导的小组发现，剩余的96%基因材料中的某些DNA对于帮助形成正确排布编译DNA的边界非常重要。他们的结果发表在7月13日的Science上。
文章第一作者，UCSD助理研究员Victoria Lunyak说：“一些垃圾DNA可以被视作标点符号，以帮助基因组实现编译。”
在老鼠中，同样只有约4%的基因拥有编译蛋白的功能，剩余的垃圾DNA不断重复且没有可编译的序列。科学家分析了一个重复的基因序列SINE B2，它位于生长激素基因位置处，这一基因和衰老及寿命有关。结果小组惊讶的发现SINE B2对于形成功能区域分界线至关重要。
功能区域含有各种管理信号以及对于激活或是压制特定基因很关键的信息。每个域都通过边界划分为实体，就类似于通过标点符号划分句子和单词。科学家的结果显示，重复的基因序列或许在哺乳动物中被广泛用于组织功能区域。
Rosenfeld说，没有边界元件，基因组的编码部分如同没有标点的段落。破译“垃圾”DNA中的信息为医学研究特别是基因治疗开辟了新的领域，有助于寻找一种向患者移植不含多余遗传序列（可能会使基因治疗失效）的基因的方法。
原文链接：http://www.physorg.com/news103469449.html
原始出处:
Science 13 July 2007:
Vol. 317. no. 5835, pp. 248 - 251
DOI: 10.1126/science.1140871
Developmentally Regulated Activation of a SINE B2 Repeat as a Domain Boundary in Organogenesis
Victoria V. Lunyak,1,2* Gratien G. Prefontaine,1
Esperanza Núñez,1 Thorsten Cramer,5 Bong-Gun Ju,1 Kenneth A. Ohgi,1 Kasey Hutt,1 Rosa Roy,4 Angel García-Díaz,4 Xiaoyan Zhu,1 Yun Yung,1 Lluís Montoliu,4 Christopher K. Glass,3 Michael G. Rosenfeld1*
The temporal and spatial regulation of gene expression in mammalian development is linked to the establishment of functional chromatin domains. Here, we report that tissue-specific transcription of a retrotransposon repeat in the murine growth hormone locus is required for gene activation. This repeat serves as a boundary to block the influence of repressive chromatin modifications. The repeat element is able to generate short, overlapping Pol II–and Pol III–driven transcripts, both of which are necessary and sufficient to enable a restructuring of the regulated locus into nuclear compartments. These data suggest that transcription of interspersed repetitive sequences may represent a developmental strategy for the establishment of functionally distinct domains within the mammalian genome to control gene activation.
1 Howard Hughes Medical Institute, School of Medicine, University of California, San Diego, 9500 Gilman Drive, Room 345, La Jolla, CA 92093–0648, USA.
2 Department of Medicine, Division of Endocrinology, University of California, San Diego, La Jolla, CA 92093, USA.
3 Department of Cellular and Molecular Medicine, Department and School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
4 Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, C/Darwin 3, 28049 Madrid, Spain.
5 Department of Hepatology and Gastroenterology, Charité Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany.
These authors contributed equally to this work.
* To whom correspondence should be addressed. E-mail: mrosenfeld@ucsd.edu (M.G.R.); vlunyak@uscd.edu (V.V.L.)
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