Department of Molecular Biology, Princeton University, Princeton, NJ 08544.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544.
Microbiol Spectr. 2014 Dec;2(6). doi: 10.1128/microbiolspec.MDNA3-0025-2014.
The ciliate Oxytricha is a microbial eukaryote with two genomes, one of which experiences extensive genome remodeling during development. Each round of conjugation initiates a cascade of events that construct a transcriptionally active somatic genome from a scrambled germline genome, with considerable help from both long and small noncoding RNAs. This process of genome remodeling entails massive DNA deletion and reshuffling of remaining DNA segments to form functional genes from their interrupted and scrambled germline precursors. The use of Oxytricha as a model system provides an opportunity to study an exaggerated form of programmed genome rearrangement. Furthermore, studying the mechanisms that maintain nuclear dimorphism and mediate genome rearrangement has demonstrated a surprising plasticity and diversity of noncoding RNA pathways, with new roles that go beyond conventional gene silencing. Another aspect of ciliate genetics is their unorthodox patterns of RNA-mediated, epigenetic inheritance that rival Mendelian inheritance. This review takes the reader through the key experiments in a model eukaryote that led to fundamental discoveries in RNA biology and pushes the biological limits of DNA processing.
纤毛虫草履虫是一种具有两个基因组的微生物真核生物，其中一个在发育过程中经历广泛的基因组重塑。每一轮的接合都启动了一系列事件，这些事件从混乱的生殖系基因组构建出一个转录活跃的体细胞基因组，长链和小非编码 RNA 都提供了相当大的帮助。这个基因组重塑的过程涉及大量的 DNA 缺失和剩余 DNA 片段的重新排列，从中断和混乱的生殖系前体形成功能基因。将草履虫作为模型系统来研究程序基因组重排的夸张形式提供了机会。此外，研究维持核二态性和介导基因组重排的机制表明，非编码 RNA 途径具有令人惊讶的可塑性和多样性，其新的作用超出了传统的基因沉默。纤毛虫遗传学的另一个方面是它们非正统的 RNA 介导的表观遗传遗传模式，这与孟德尔遗传相媲美。这篇综述带读者了解了在模型真核生物中进行的关键实验，这些实验导致了 RNA 生物学的重大发现，并推动了 DNA 处理的生物学极限。
