Gene silencing by RNAi and DNA Methylation

转录后基因沉默(PTGS)是由双链RNA(RNAi)或反义RNA表达引起的表观遗传现象。尽管部分分子机制已知，但这种调控的机制在很大程度上还没有解决。转导转录因子基因沉默(TGS)存在于哺乳动物的印迹和共抑制中。在这两种情况下，都可以观察到不同的DNA去重新甲基化。在植物中，小的双链(DS)RNA似乎指定了要甲基化的DNA靶标。TGS和PTGS在植物中的相关性被提出，并在当前被广泛讨论。在哺乳动物中，反义转录物存在于多个(如果不是全部)印迹基因上，从而为dsRNA的形成和潜在的RNA介导的DNA甲基化提供了先决条件。在该项目的第一部分，我们想要在功能上表征模式生物Dictyostelius中RNAi机制的已知组件，并确定更多的组件。这是基于先前对Dictyostelials中RNAi的研究以及对三个RdRP和两个DICER同源物的鉴定。在该项目的第二部分，我们想通过分析最近发现的一种Dictyostoma甲基转移酶(DNMT2同源基因)的功能，特别是与小dsRNA相关的功能，进入TGS领域。在施沃朋克计划的框架内，这两个项目的数据将应用于其他模型系统，并与之进行比较(人类细胞培养、植物、果蝇)。

Posttranscriptionel Genesilencing (PTGS) is an epigenetic phenomenon which is elicited by double stranded RNA (RNAi) or the expression of antisense-RNA. Though parts of the molecular machinery are known, the mechanisms of this regulation are largely unsolved. Transkriptionel genesilencing (TGS) is found e.g. in mammalian imprinting and in cosuppression in. In both cases, differential de-novo methylation of DNA is observed. In plants, small double stranded (ds)RNAs appear to specify the DNA target to be methylated. A correlation between TGS and PTGS in Plants is suggested and currently intensely discussed. In mammals, antisense transcripts are found at several if not all imprinting loci thus providing teh prerequisites for the formation of dsRNA and a potential RNA mediated DNA methylation. In the first part of the project we want to functionally characterize known components of the RNAi machinery in the model organism Dictyostelium and to identify further components. This is based on the previous work on RNAi in Dictyostelium and the identification of three RdRP and two dicer homologs. In the second part of the project we would like to enter the TGS field by analyzing the function of a recently identified Dictyostelium methyltransferase (Dnmt2 homolog), especially in relation to small dsRNAs. In the frame of the Schwerpunktprogramm, data from both projects will be applied in and compared to other model systems (human cell culture, plants, Drosophila).