Pirritano Marcello, Götz Ulrike, Karunanithi Sivarajan, Nordström Karl, Schulz Marcel H, Simon Martin
Molecular Cell Dynamics, Centre for Human and Molecular Biology, Saarland University, 66123 Saarbrücken, Germany.
Cluster of Excellence, Multimodal Computing and Interaction, Saarland University and Department for Computational Biology and Applied Algorithmics, Max Planck Institute for Informatics, Saarland Informatics Campus, 66123 Saarbrücken, Germany.
Genes (Basel). 2018 Feb 21;9(2):117. doi: 10.3390/genes9020117.
Genes or alleles can interact by small RNAs in a homology dependent manner meaning that short interfering (siRNAs) can act in at the chromatin level producing stable and heritable silencing phenotypes. Because of the puzzling data on endogenous paramutations, their impact contributing to adaptive evolution in a Lamarckian manner remains unknown. An increasing number of studies characterizes the underlying siRNA accumulation pathways using transgene experiments. Also in the ciliate , we induce silencing on the chromatin level by injection of truncated transgenes. Here, we characterize the efficiency of this mechanism at different temperatures showing that silencing of the endogenous genes is temperature dependent. Analyzing different transgene constructs at different copy numbers, we dissected whether silencing efficiency is due to varying precursor RNAs or siRNA accumulation. Our data shows that silencing efficiency correlates with more efficient accumulation of primary siRNAs at higher temperatures rather than higher expression of precursor RNAs. Due to higher primary levels, secondary siRNAs also show temperature dependency and interestingly increase their relative proportion to primary siRNAs. Our data shows that efficient silencing on the chromatin level in depends on environmental parameters, thus being an important epigenetic factor limiting regulatory effects of siRNAs.
基因或等位基因可以通过小RNA以同源依赖的方式相互作用，这意味着短干扰RNA（siRNA）可以在染色质水平起作用，产生稳定且可遗传的沉默表型。由于关于内源性副突变存在令人困惑的数据，它们以拉马克方式对适应性进化的影响仍然未知。越来越多的研究通过转基因实验来表征潜在的siRNA积累途径。同样在纤毛虫中，我们通过注射截短的转基因在染色质水平诱导沉默。在这里，我们表征了该机制在不同温度下的效率，表明内源基因的沉默是温度依赖性的。分析不同拷贝数的不同转基因构建体，我们剖析了沉默效率是由于前体RNA的变化还是siRNA的积累。我们的数据表明，沉默效率与较高温度下初级siRNA更有效的积累相关，而不是前体RNA的较高表达。由于初级水平较高，次级siRNA也表现出温度依赖性，有趣的是，它们相对于初级siRNA的相对比例增加。我们的数据表明，在纤毛虫中染色质水平上的有效沉默取决于环境参数，因此是限制siRNA调节作用的重要表观遗传因素。
