Panoramix enforces piRNA-dependent co-transcriptional silencing (GRO-Seq)

The Piwi-interacting RNA (piRNA) pathway is a small RNA-based innate immune system that defends germ cell genomes against transposons. In Drosophila ovaries, the nuclear Piwi protein is required for transcriptional silencing of transposons, though the precise mechanisms by which this occurs are unknown. Here we show that CG9754 is a component of Piwi complexes that functions downstream of Piwi and its binding partner, Asterix, in transcriptional silencing. Enforced tethering of CG9754 protein to nascent mRNA transcripts causes co-transcriptional silencing of the source locus and the deposition of repressive chromatin marks. We have named CG9754 Panoramix, and propose that this protein could act as an adaptor, scaffolding interactions between the piRNA pathway and the general silencing machinery that it recruits to enforce transcriptional repression. Examination of nascent transcripts from germline knockdown of either Piwi or CG9754 from Drosophila ovaries

Piwi互作RNA（Piwi-interacting RNA，piRNA）通路是一类基于小型RNA的先天免疫系统，可保护生殖细胞基因组免受转座子侵扰。在果蝇卵巢中，核内Piwi蛋白对于转座子的转录沉默是必需的，但其具体作用机制尚不明确。本研究证实CG9754是Piwi复合物的组分之一，其在Piwi及其结合蛋白Asterix的下游参与转录沉默过程。将CG9754蛋白强制锚定至新生mRNA转录本，会导致其来源基因座发生共转录沉默，并沉积抑制性染色质修饰。我们将CG9754命名为Panoramix，并提出该蛋白可作为衔接蛋白，搭建piRNA通路与所招募的通用沉默机器之间的相互作用支架，以实现转录抑制。对果蝇卵巢中Piwi或CG9754生殖系敲低后的新生转录本进行的检测