CHROMOSOMAL TELOMERES IN DROSOPHILA

真核生物染色体的末端称为端粒， 重要功能。其中一个功能是自我维持;因为DNA的丢失 是复制中固有的，这种损失必须是 通过在末端添加端粒DNA来平衡。很长的- 本研究的长期目标是了解 果蝇端粒，它们是如何维持的，以及它们是如何发挥作用的。它 果蝇端粒似乎是由一种新的机制维持的， 包括偶尔转移到特化的 非LTR反转录转座子家族。非LTR反转录转座子， 称为LINE，是一类移动的元素， 后生动物，并已牵连在造成突变的人。两个 端粒相关LINE家族，HeT-A和TART，已经在 果蝇该项目的一个长期目标是确定 这是这些元素不寻常的换位特异性的基础。一 本申请中提出具体目的是显示HeT-A和TART 元件位于果蝇染色体的末端， 与这些元件的DNA探针杂交的末端DNA片段。一 第二个目标是调查数量，DNA序列组织， TART元件在D.黑腹菌和其他 果蝇属。这将通过基因组Southern印迹来完成 分析、原位杂交和DNA克隆。第三个目标是 分析了TART基因在D.黑腹菌转录 单位和启动子将被定位。的组织和发育阶段 TART的转录和翻译产物的积累将 也要坚决。第四个目标是重新引入克隆的TART元件 导入D.黑腹，并表明它将转置到一个 端粒这将为将来的转座试验提供体内转座试验。 体外诱变实验。

The ends of eukaryotic chromosomes, called telomeres, perform several vital functions. One function is self-maintenance; because loss of DNA from the terminus is inherent in replication, this loss must be counterbalanced by addition of telomeric DNA to the terminus. The long- term goal of the research proposed here is to understand the structure of Drosophila telomeres, how they are maintained, and how they function. It appears that Drosophila telomeres are maintained by a novel mechanism involving the occasional transposition to the terminus of specialized families of non-LTR retrotransposons. Non-LTR retrotransposons, also called LINEs, are a class of mobile elements which is ubiquitous among metazoans and has been implicated in causing mutations in man. Two families of telomere-associated LINEs, HeT-A and TART, have been found in Drosophila. A long-term objective of this project is to determine the basis for the unusual transpositional specificity of these elements. One specific aim proposed in this application is to show that HeT-A and TART elements are at the termini of Drosophila chromosomes by identifying terminal DNA fragments hybridizing with DNA probes for these elements. A second aim is to survey the number, DNA sequence organization, and chromosomal locations of TART elements in D. melanogaster and other Drosophila species. This will be accomplished by genomic Southern blot analysis, in situ hybridization, and DNA cloning. A third aim is to characterize the expression of TART in D. melanogaster. The transcription unit and promoter will be mapped. The tissues and developmental stages in which the transcription and translation products of TART accumulate will also be determined. The fourth aim is to reintroduce a cloned TART element into the germline of D. melanogaster and show that it will transpose to a telomere. This would provide an in vivo transposition assay for future in vitro mutagenesis experiments.