School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.
World Research Hub Initiative, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.
Genes Cells. 2021 May;26(5):298-312. doi: 10.1111/gtc.12840. Epub 2021 Mar 19.
In eukaryotic nuclei, a number of phase-separated nuclear bodies (NBs) are present. RNA polymerase II (Pol II) is the main player in transcription and forms large condensates in addition to localizing at numerous transcription foci. Cajal bodies (CBs) and histone locus bodies (HLBs) are NBs that are involved in transcriptional and post-transcriptional regulation of small nuclear RNA and histone genes. By live-cell imaging using human HCT116 cells, we here show that Pol II condensates (PCs) nucleated near CBs and HLBs, and the number of PCs increased during S phase concomitantly with the activation period of histone genes. Ternary PC-CB-HLB associates were formed via three pathways: nucleation of PCs and HLBs near CBs, interaction between preformed PC-HLBs with CBs and nucleation of PCs near preformed CB-HLBs. Coilin knockout increased the co-localization rate between PCs and HLBs, whereas the number, nucleation timing and phosphorylation status of PCs remained unchanged. Depletion of PCs did not affect CBs and HLBs. Treatment with 1,6-hexanediol revealed that PCs were more liquid-like than CBs and HLBs. Thus, PCs are dynamic structures often nucleated following the activation of gene clusters associated with other NBs.
在真核细胞核中，存在许多相分离的核体（NBs）。RNA 聚合酶 II（Pol II）是转录的主要参与者，除了定位于许多转录焦点外，还形成大型凝聚体。Cajal 体（CBs）和组蛋白基因座体（HLBs）是参与小核 RNA 和组蛋白基因转录和转录后调控的 NBs。通过使用人 HCT116 细胞的活细胞成像，我们在这里表明，Pol II 凝聚体（PCs）在 CB 和 HLB 附近成核，并且在 S 期期间，随着组蛋白基因的激活期，PC 的数量增加。通过三种途径形成了三元 PC-CB-HLB 缔合物：在 CB 附近成核的 PCs 和 HLBs、预形成的 PC-HLBs 与 CB 之间的相互作用以及在预形成的 CB-HLB 附近成核的 PCs。Coilin 敲除增加了 PCs 和 HLBs 之间的共定位率，而 PC 的数量、成核时间和磷酸化状态保持不变。PCs 的耗竭不影响 CBs 和 HLBs。用 1,6-己二醇处理表明，PCs 比 CBs 和 HLBs 更具有液态样性质。因此，PCs 是动态结构，通常在与其他 NBs 相关的基因簇激活后成核。
