Wang Chen, Ma Hanhui, Baserga Susan J, Pederson Thoru, Huang Sui
Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL.
Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA.
bioRxiv. 2023 Mar 31:2023.03.30.534966. doi: 10.1101/2023.03.30.534966.
The nucleolus is a multi-functional nuclear body. To tease out the roles of nucleolar structure without resorting to multi-action drugs, we knocked down RNA polymerase I subunit RPA194 in HeLa cells by siRNA. Loss of RPA194 resulted in nucleolar structural segregation and effects on both nucleolus-proximal and distal nuclear components. The perinucleolar compartment was disrupted, centromere-nucleolus interactions were significantly reduced, and the intranuclear locations of specific genomic loci were altered. Moreover, Cajal bodies, distal from nucleoli, underwent morphological and compositional changes. To distinguish whether these global reorganizations are the results of nucleolar structural disruption or inhibition of ribosome synthesis, the pre-ribosomal RNA processing factor, UTP4, was also knocked down, which did not lead to nucleolar segregation, nor the intranuclear effects seen with RPA195A knockdown, demonstrating that they do not arise from a cessation of ribosome synthesis. These findings point to a commutative system that links nucleolar structure to the maintenance and spatial organization of certain nuclear bodies and genomic loci.
核仁是一种多功能的细胞核结构。为了在不使用多作用药物的情况下探究核仁结构的作用，我们通过小干扰RNA（siRNA）敲低了HeLa细胞中的RNA聚合酶I亚基RPA194。RPA194的缺失导致核仁结构分离，并对核仁近端和远端的核成分产生影响。核仁周围区室被破坏，着丝粒与核仁的相互作用显著减少，特定基因组位点的核内位置发生改变。此外，远离核仁的卡哈尔体在形态和组成上也发生了变化。为了区分这些整体重组是核仁结构破坏还是核糖体合成抑制的结果，我们还敲低了核糖体前体RNA加工因子UTP4，结果并未导致核仁分离，也未出现敲低RPA195A时所观察到的核内效应，这表明这些变化并非由核糖体合成的停止引起。这些发现指向了一个将核仁结构与某些核体及基因组位点的维持和空间组织联系起来的交换系统。
