Gruchota Julita, Denby Wilkes Cyril, Arnaiz Olivier, Sperling Linda, Nowak Jacek K
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.
Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, University of Paris Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France.
Nucleic Acids Res. 2017 May 5;45(8):4722-4732. doi: 10.1093/nar/gkw1318.
Spt5 is a conserved and essential transcriptional regulator that binds directly to RNA polymerase and is involved in transcription elongation, polymerase pausing and various co-transcriptional processes. To investigate the role of Spt5 in non-coding transcription, we used the unicellular model Paramecium tetraurelia. In this ciliate, development is controlled by epigenetic mechanisms that use different classes of non-coding RNAs to target DNA elimination. We identified two SPT5 genes. One (STP5v) is involved in vegetative growth, while the other (SPT5m) is essential for sexual reproduction. We focused our study on SPT5m, expressed at meiosis and associated with germline nuclei during sexual processes. Upon Spt5m depletion, we observed absence of scnRNAs, piRNA-like 25 nt small RNAs produced at meiosis. The scnRNAs are a temporal copy of the germline genome and play a key role in programming DNA elimination. Moreover, Spt5m depletion abolishes elimination of all germline-limited sequences, including sequences whose excision was previously shown to be scnRNA-independent. This suggests that in addition to scnRNA production, Spt5 is involved in setting some as yet uncharacterized epigenetic information at meiosis. Our study establishes that Spt5m is crucial for developmental genome rearrangements and necessary for scnRNA production.
Spt5是一种保守且必需的转录调节因子，它直接与RNA聚合酶结合，并参与转录延伸、聚合酶暂停及各种共转录过程。为了研究Spt5在非编码转录中的作用，我们使用了单细胞模型草履虫。在这种纤毛虫中，发育由表观遗传机制控制，该机制利用不同类别的非编码RNA来靶向DNA消除。我们鉴定出两个SPT5基因。一个（STP5v）参与营养生长，而另一个（SPT5m）对有性生殖至关重要。我们的研究重点是在减数分裂时表达且在有性过程中与生殖细胞核相关的SPT5m。在耗尽Spt5m后，我们观察到scnRNA缺失，scnRNA是在减数分裂时产生的类似piRNA的25个核苷酸的小RNA。scnRNA是生殖系基因组的临时拷贝，在编程DNA消除中起关键作用。此外，耗尽Spt5m会消除所有生殖系限制序列的消除，包括其切除先前已显示与scnRNA无关的序列。这表明除了scnRNA产生外，Spt5还参与在减数分裂时设置一些尚未表征的表观遗传信息。我们的研究表明，Spt5m对发育基因组重排至关重要，对scnRNA产生是必需的。
