An evolutionary approach to the structure and activities of group II introns

II组内含子结构和活性的进化方法

• 批准号: 203717-2012
• 负责人: Zimmerly, Steven
• 金额: $ 2.91万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2013
• 资助国家: 加拿大
• 起止时间: 2013-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=523525
• 关键词: evolutionary; approach; structure; activities; group

Group II introns are novel genetic elements that possess properties of both catalytic RNAs and retroelements. The introns consist of two components: 1) a catalytic RNA (ribozyme) component that carries out a self-splicing reaction; and 2) an intron-encoded reverse transcriptase (RT) that facilitates the splicing reaction and allows the introns to insert into new genomic locations through a retrotransposition (i.e., reverse transcription) mechanism. This remarkable and coordinated series of reactions by the ribozyme and RT is itself worthy of study; however, group II introns have attracted additional attention because of their relationships to other important eukaryotic elements. The ribozyme of group II introns is widely believed to be the ancestor of spliceosomal introns (~25% of the human genome), while the RT is related to RTs of retroelements, retroviruses and telomerase. Group II introns are considered ancestral to non-LTR retroelements (~20% of the human genome), as well as spliceosomal introns. Because group II introns are relatively simple systems (two molecules), studying their mechanisms is expected to shed light on spliceosomal introns and non-LTR retroelements, as has been the case in the past. This application proposes to continue the research program of my lab, in which we use a comparative approach to address the breadth of group II intron structures and properties, as well as the evolutionary development and differentiation of the introns. Specific aims are: 1) to extend phylogenetic studies of group II intron sequences to reconstruct a more complete history of the introns; 2) to use sequence covariation data to infer RNA structural information about differentiated subclasses of introns, and to test validity of the predictions experimentally; 3) to biochemically investigate self-splicing properties of the IIC intron B.h.I1; and 4) to address the three-dimensional RNA structures of subclasses of group II introns through modeling and biochemical experimentation. Together these studies will advance our understanding of the mechanisms of a unique genetic element, and help elucidate how the introns evolved and eventually proliferated to occupy a large fraction of eukaryotic genomes.

II 组内含子是新型遗传元件，具有催化 RNA 和逆转录元件的特性。内含子由两个组件组成：1）催化RNA（核酶）组件，进行自我剪接反应； 2）内含子编码的逆转录酶（RT），其促进剪接反应并允许内含子通过逆转录转座（即逆转录）机制插入新的基因组位置。核酶和 RT 所发生的一系列显着且协调的反应本身就值得研究；然而，第二组内含子由于与其他重要的真核元件的关系而引起了额外的关注。 II组内含子的核酶被广泛认为是剪接体内含子（约占人类基因组的25%）的祖先，而RT与逆转录元件、逆转录病毒和端粒酶的RT相关。 II 组内含子被认为是非 LTR 逆转录元件（约占人类基因组的 20%）以及剪接体内含子的祖先。由于 II 组内含子是相对简单的系统（两个分子），因此研究其机制有望揭示剪接体内含子和非 LTR 逆转录因子，就像过去的情况一样。该申请建议继续我的实验室的研究计划，其中我们使用比较方法来解决第二组内含子结构和特性的广度，以及内含子的进化发展和分化。具体目标是：1）扩展II组内含子序列的系统发育研究，以重建更完整的内含子历史； 2）利用序列共变数据推断内含子差异亚类的RNA结构信息，并通过实验检验预测的有效性； 3) 生化研究IIC内含子B.h.I1的自剪接特性； 4) 通过建模和生化实验来研究 II 组内含子亚类的三维 RNA 结构。这些研究将共同​​推进我们对独特遗传元件机制的理解，并有助于阐明内含子如何进化并最终增殖以占据真核基因组的很大一部分。