预-rRNA在雄性生殖细胞的XY体内抑制基因转录

Abstract

Nucleolus is disassembled when the nuclear envelope breaks down during mitosis prophase. However, the dynamics of nucleolus in meiotic prophase remain unclear. Here, by tracking nucleolar components, we show that nucleolus is fragmented even before the breakdown of the nuclear envelope. Instead of dissolving in nucleoplasm or cytoplasm, the nucleolar components are reaggregated and fuse with the XY body during the prophase I of meiosis. The dynamic relocation of the nucleolar components to the XY body is governed by the ATR-dependent signaling pathway. Moreover, the relocated pre-rRNA covers the entire X and Y chromosomes. The treatment with RNA polymerase I inhibitor BMH-21 only disrupts the accumulation of pre-ribosomal RNA (pre-rRNA) but not other nucleolar components on the X and Y chromosomes. Surprisingly, this disruption of pre-rRNA induces the recruitment of RNA polymerase II to the XY body and partially abolishes meiotic sex chromosome inactivation (MSCI). Taken together, this study reveals pre-rRNA as a key epigenetic regulator for MSCI.Both nucleolus and the XY body are nuclear membraneless condensates. In this study, we show that nucleoli fuse with the XY body during the prophase I of meiosis in the male germ cells, providing the evidence that two different nuclear bodies fuse together in a dynamic process. Moreover, associated with the fusion, pre-rRNA relocates onto the X and Y chromosomes, acting as non-coding RNA to occupy gene regions and represses gene transcription in the sex chromosomes. Thus, this study reveals that the products from RNA polymerase I-meditated transcription repress RNA polymerase II-meditated gene transcription.