MOLECULAR BASIS OF HYBRID DYSGENESIS IN DROSOPHILA

我们建议以果蝇为模型系统来研究其作用机制 参与控制反转录转座子的动员。我们将利用 一种杂交不育系统，在该系统中， 特定的德氏杆菌菌株导致生殖系移动 不同的转座子。其中之一是Penelope元素，它基于 在几条间接证据上，似乎是原因 这一现象的动因。Penelope是一个2.7kb的分子，其两侧是690个碱基对 反向重复序列，包含一个开放阅读框架，能够 编码一种与猪瘟病毒逆转录酶同源的蛋白质 逆转录病毒。在这些杂交中动员的第二个特征性元素 是含有LTR的Ulysses反转录转座子。我们的第一步是 分析将证明佩内洛普能够动员其他人 种系转化黑腹果蝇后的转座因子。 实验将被设计来确定佩内洛普的单个副本是否 足以促进其动员或佩内洛普的多个副本，或 在热休克促进剂的控制下，单拷贝是必要的 以达到这一效果。然后我们将分析Penelope是否编码一个 酶活性逆转录酶以及该元件是否可以 通过逆转录机制移动。基因的分子基础 将分析不育杂交后代的佩内洛普动员情况 通过对S编码的核糖核酸和S编码的蛋白质的种系分布进行了研究 在发育不良果蝇过程中的这一因素。 提案的第二部分将集中分析 Ulysses含LTR反转录转座子的动员机制。 该元件在发育不良果蝇的种系中的表达将是 分析评估高频率动员的可能性 是由于Ulysses编码的转录/翻译增加 产品。然后我们将检验尤利西斯动员是 由于尤利西斯VLP使用Penelope编码的逆转录酶。 将使用体外系统测试替代可能性，以 测量发育不良果蝇种系中存在的VLP的能力 尤利西斯DNA的体外直接整合。

We propose to use Drosophila as a model system to study the mechanisms involved in the control of retrotransposon mobilization. We will exploit a hybrid dysgenesis system in which unidirectional crosses between two specific strains of D. virilis result in the germline movement of different transposons. One of them is the Penelope element which, based on several lines of circumstantial evidence, seems to be the causative agent of this phenomenon. Penelope is a 2.7 kb element flanked by 690 bp inverted repeats and containing one open reading frame capable of encoding a protein homologous to the reverse transcriptase of retroviruses. A second characterized element mobilized in these crosses is the LTR-containing Ulysses retrotransposon. The first step in our analysis will be to demonstrate that Penelope is able to mobilize other transposable elements after germline transformation into D. melanogaster. Experiments will be designed to determine if a single copy of Penelope is sufficient to promote its mobilization or multiple copies of Penelope, or a single copy under the control of a heat shock promoter, are necessary to obtain this effect. We will then analyze whether Penelope encodes an enzymatically active reverse transcriptase and whether this element can move by a reverse transcription mechanism. The molecular basis for Penelope mobilization in the progeny of dysgenic crosses will be analyzed by studying the germline distribution of RNA(s) and protein(s) encoded by this element during the development of dysgenic flies. The second part of the proposal will concentrate on the analysis of the mechanisms of mobilization of the Ulysses LTR-containing retrotransposon. The expression of this element in the germline of dysgenic flies will be analyze to evaluate the possibility that high frequency of mobilization is due to increased transcription/translation of Ulysses-encoded products. We will then test the hypothesis that Ulysses mobilization is due to the use of Penelope-encoded reverse transcriptase by Ulysses VLPs. Alternative possibilities will be tested using an in vitro system to measure the ability of VLPs present in the germline of dysgenic flies to direct in vitro integration of Ulysses DNA.