HET-A, A RETROPOSON WITH A ROLE IN CHROMOSOME STRUCTURE

HET-A，一种在染色体结构中发挥作用的反座子

• 批准号: 2188063
• 负责人: MARY-LOU PARDUE
• 金额: $ 20.54万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-03-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2188063
• 关键词: DNA; Drosophilidae; RNA; autoradiography; cell type; gene expression; genetic mapping; genetic transcription; heterochromatin; immunofluorescence technique; in situ hybridization; northern blottings; nucleic acid probes; nucleic acid sequence; protein structure function; telomere; tissue /cell culture; transposon /insertion element; western blottings

We have identified a new class of DNA sequences that are found only in heterochromatin, yet' differ significantly from the tandemly repeated DNAs previously characterized as heterochromatin-specific sequences. This new class of sequences, the HeT DNA family, is from Drosophila melanogaster. The polytene chromosomes plus the many chromosomal rearrangements and marker mutations that are available make D. melanogaster the best model system for studying the structure and function of heterochromatin; however we believe that the results of these studies will give insights into the chromosomes of all metazoa. A major component of HeT DNA is a transposable element named HeT-A. Although HeT-A elements are associated with sequences that are shared between telomeric and pericentric heterochromatin (sequences that make up other components of HeT DNA), HeT-A elements themselves are found only in telomeric heterochromatin. HeT-A elements have been added to the broken ends of the ten "healed" terminal deletions now known in D. melanogaster. The elements have apparently been added by transposition events involving no sequence homology, instead the structure of the junction with the broken chromosome suggests retrotransposition. If this is true, the retrotransposition is remarkably restricted.- HeT-A elements differ from the known transposable elements in having >2 kb of conserved short-range sequence repeats on one end (the end that invariably is attached to the broken chromosome end). HeT-A elements are abundant on the telomeres of unbroken chromosomes. These features of HeT-A elements suggest that, although they are transposable elements, they may have a structural role in telomere organization or maintenance. HeT-A elements do not resemble the very short repeats found at the telomeres in other organisms but they appear to be similar to the "telomere-associated" sequences found in metazoan chromosomes. Thus other organisms may also have transposable elements that are not "selfish DNA". We propose to characterize the protein encoded by HeT-A and any RNAs transcribed from the element. There is reason to think that transposition is inducible. We will seek to determine in what cell types and under what conditions RNA and protein are expressed as a step toward understanding the induction of transposition. We will seek HeT-A elements in a second Drosophila species to analyze the evolutionarily conserved features of the element. We propose several transgenic experiments to test conclusions about possible functions of the protein encoded by HeT-A and of the non-coding repeated segment. Finally, we will attempt to use the sequences that we define to construct functional Drosophila mini- chromosomes. These chromosomes will also allow direct tests of conclusions.

我们已经发现了一类新的DNA序列，它们只存在于 异染色质，但“显着不同，从串联重复 先前被表征为异染色质特异性序列的DNA。这 一类新的序列，HeT DNA家族，来自果蝇 黑腹菌多线染色体加上许多染色体 重排和标记突变使D. melanogaster是研究其结构的最佳模型系统， 异染色质的功能;然而，我们认为，这些结果 这些研究将使我们深入了解所有后生动物的染色体。 HeT DNA的主要成分是一个名为HeT-A的转座因子。 虽然HeT-A元件与共享的序列相关， 端粒异染色质和臂间异染色质（ HeT DNA的其他成分），HeT-A元件本身只被发现 在端粒异染色质中。HeT-A元素已被添加到 10个“愈合的”末端缺失的断裂末端，现在已知在D. 黑腹菌这些元素显然是通过换位添加的 不涉及序列同源性的事件，而不是 与断裂染色体的连接表明反转录转座。如果这 是真的，反转录是非常有限的。HeT-A元素 与已知的转座因子的不同之处在于具有> 2kb的保守的 短距离序列在一端重复（总是在 连接到断裂的染色体末端）。HeT-A元素在 完整染色体的端粒。HeT-A元素的这些特征 这表明，虽然它们是转座因子，但它们可能具有 在端粒组织或维持中的结构作用。HeT-A元素 不像在端粒中发现的非常短的重复序列， 生物体，但它们似乎类似于“端粒相关” 在后生动物染色体中发现的序列。因此，其他生物也可能 有转座因子不是“自私的DNA” 我们建议表征HeT-A和任何RNA编码的蛋白质 从元素中转录出来。我们有理由认为 是可诱导的。我们将试图确定在什么样的细胞类型和下 RNA和蛋白质的表达是理解 转座的诱导我们马上要寻找HeT-A元素 果蝇物种的进化保守特征分析 元素。我们提出了几个转基因实验来测试 关于HeT-A编码蛋白的可能功能的结论， 非编码重复片段的长度。最后，我们将尝试使用 我们定义的序列来构建功能性的果蝇迷你- 染色体这些染色体也将允许直接测试 结论.