DROSOPHILA TELOMERES--GENE, TRANSCRIPTS, AND CHROMATIN

果蝇端粒——基因、转录本和染色质

• 批准号: 6519560
• 负责人: MARY-LOU PARDUE
• 金额: $ 21.79万
• 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 2003-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6519560
• 关键词: Drosophilidae; arthropod genetics; gene expression; genetic regulation; heterochromatin; in situ hybridization; molecular cloning; nucleic acid repetitive sequence; nucleic acid sequence; protein structure function; telomere; tissue /cell culture; transfection; transposon /insertion element

Telomere sequences and their regulation have been implicated in- both cellular aging and the development of cancer; however, it is clear that these relationships are not as simple as first thought. Drosophila is a valuable model for the study of telomeres because this organism maintains its telomeres by a variation of the mechanism used by most other species. Drosophila telomeres are composed of multiple repeats of the telomere specific non-LTR retrotransposons, HeT-A and TART, rather than the simple repeats generated by telomerase. Comparison of similarities and differences between these two mechanisms offers a powerful approach for determining the essential features of telomere activity, a long term goal of our work. A primary goal of these experiments is to understand the regulation of these retrotransposons. One line of experiments will focus on the recently identified HeT-A promoter. This promoter is interesting not only for its role in telomere maintenance, but because it is the first heterochromatic promoter studied at the molecular level. Additionally, it is an unexpected intermediate between the typical promoters for non-LTR and LTR elements, a finding with evolutionary implications vis a vis retroviruses. Studies in cultured cells have detected several functional elements within the promoter sequence. This work will be extended to clearly define each element, to test the promoter by using reporter transgenes in intact flies, to identify any tissue-specific elements in the promoter, and to explore interactions with both heterochromatic and euchromatic chromosomal environments. TART yields both sense and antisense transcripts. The antisense promoter transcript was identified; it and the sense promoter will be defined. Both are heterochromatic and will be characterized as was the HeT-A promoter. HeT-A expression is dramatically increased in older flies and some cell cultures. We hypothesize that this is due to age-related changes in heterochromatin and will test this and the effects of factors affecting position effect variegation on the expression of the HeT-A and TART promoters. The origin of a novel related reverse transcriptase mRNA will be determined. Evidence suggests that this RNA is either a processed product of TART or the mRNA from a "free-standing" cellular gene. This mRNA is interesting because of a possible evolutionary relationship to the catalytic subunit of telomerase. The phylogenetic study of the transposon mechanism for telomere maintenance will be extended to include insects outside the genus Drosophila to broaden the view of its essential features of this mechanism.

端粒序列及其调节与细胞衰老和癌症的发展有关;然而，很明显，这些关系并不像最初想象的那么简单。果蝇是研究端粒的一个有价值的模型，因为这种生物体通过大多数其他物种所使用的机制的变化来维持其端粒。果蝇端粒由端粒特异性非LTR反转录转座子HeT-A和TART的多个重复序列组成，而不是由端粒酶产生的简单重复序列。比较这两种机制之间的相似性和差异性，为确定端粒活动的基本特征提供了一种强有力的方法，这是我们工作的长期目标。这些实验的主要目的是了解这些逆转录转座子的调节。一系列实验将集中在最近鉴定的HeT-A启动子上。这个启动子不仅因为它在端粒维持中的作用而有趣，而且因为它是第一个在分子水平上研究的异染色质启动子。此外，它是非LTR和LTR元件的典型启动子之间的一个意想不到的中间体，这一发现维斯逆转录病毒具有进化意义。在培养细胞中的研究已经检测到启动子序列中的几个功能元件。这项工作将被扩展到明确定义每个元素，测试的启动子，通过使用报告转基因在完整的苍蝇，以确定任何组织特异性元件的启动子，并探讨与异染色质和常染色质染色体环境的相互作用。TART产生有义和反义转录本。鉴定了反义启动子转录物;将对反义启动子和有义启动子进行定义。 两者都是异染色质的，并且将被表征为HeT-A启动子。HeT-A表达在老年果蝇和一些细胞培养物中显著增加。我们假设，这是由于异染色质的年龄相关的变化，并将测试这一点和影响的HeT-A和TART启动子的表达的位置效应杂色的因素的影响。将确定一种新的相关逆转录酶mRNA的来源。有证据表明，这种RNA要么是TART的加工产物，要么是来自“独立”细胞基因的mRNA。这种mRNA是有趣的，因为一个可能的进化关系，端粒酶的催化亚基。端粒维持转座子机制的系统发育研究将扩展到果蝇属以外的昆虫，以拓宽对该机制基本特征的认识。