Structure, function and evolution of small RNAs in unicellular eukaryotes

核糖核酸(RNA)分子称为非编码RNA(NcRNAs)，具有不同的功能，控制着所有生物体中的各种细胞过程。许多真核生物基因组中含有更多的基因组DNA序列，这些DNA序列指定的是ncRNAs的产生，而不是特定的蛋白质，然而，大多数这些ncRNAs的详细功能仍然不清楚。因此，识别和确定ncRNAs的功能正成为功能基因组学-将基因组DNA序列与生物功能联系起来-的一个日益重要的领域，也是我的研究计划的主要目标。我们将研究被称为原生生物的单细胞真核生物中的ncRNA，原生生物构成了真核生物进化多样性的主体。诺贝尔奖获奖发现是首次在原生动物中表征ncRNAs及其细胞功能的结果，例如自剪接(自催化)内含子和端粒酶RNA，这两者都是首次在嗜热四膜虫中发现的。我们将研究的两类主要的ncRNA是小核仁(Sno)和小核(Sn)RNA。众所周知，snoRNAs在核糖体的合成中具有功能作用--核糖体是负责细胞内蛋白质合成的复合体。我们将使用体内方法来确定单个snoRNAs在核糖体合成过程中在原生生物Euglena gracilis中的特定作用，Euglena gracilis是一种具有特别复杂的核糖体组装途径的生物。单链RNA是真核生物特有的细胞结构(S)的核心组成部分，被称为剪接体。剪接体是从蛋白质编码的RNA中移除中间序列(内含子)所必需的，这一过程被称为剪接。我们将描述早期分化的原生蓝氏贾第鞭毛虫的剪接和剪接体成分。这种生物特别有趣，因为它拥有一种非常不寻常的剪接系统，含有相对较少的内含子，随着它缩小基因组大小并进一步适应其寄生生活方式，似乎正在经历内含子的丢失。我们还将描述这些原生生物中用于ncRNA合成的基因表达途径和细胞成分，并利用它们的进化地位来获得关于真核生物中ncRNA和剪接体进化的见解。

Ribonucleic acid (RNA) molecules called non-coding RNAs (ncRNAs) have diverse functions, controlling a variety of cellular processes in all organisms. Many eukaryotic genomes contain more genomic DNA sequence specifying the production of ncRNAs than specifying proteins and yet, the detailed function of most of these ncRNAs remains unknown. Consequently, identifying and determining functions of ncRNAs is becoming an increasingly important area of functional genomics - relating genomic DNA sequence to biological function - and is a primary objective of my research program. We will study ncRNAs in the unicellular eukaryotes called protists, organisms that comprise the bulk of eukaryotic evolutionary diversity. Nobel prize-winning discoveries were the result of first characterizing ncRNAs and their cellular functions in protists, such as self-splicing (autocatalytic) introns and telomerase RNA, both first identified in Tetrahymena thermophila. Two main classes of ncRNAs that we will investigate are the small nucleolar (sno) and small nuclear (sn) RNAs. SnoRNAs are known to have a functional role in the synthesis of ribosomes - the complexes responsible for protein synthesis in the cell. We will use an in vivo approach to determine the specific roles of individual snoRNAs during ribosome synthesis in the protist Euglena gracilis, an organism with a particularly complex ribosome assembly pathway. SnRNAs are core components of the eukaryote-specific cellular structure(s) termed the spliceosome. Spliceosomes are required for the removal of intervening sequences (introns) from protein-coding RNAs, a process called splicing. We will characterize splicing and spliceosome components in the early-diverging protist Giardia lamblia. This organism is particularly interesting because it possesses a very unusual splicing system, contains relatively few introns, and appears to be undergoing intron loss as it reduces its genome size and further adapts to its parasitic lifestyle. We will also characterize gene expression pathways and cellular components used for ncRNA synthesis in these protists, and exploit their evolutionary positions to derive insights about ncRNA and spliceosome evolution in eukaryotes.