McIntyre Alexa B R, Tschan Adrian Beat, Meyer Katrina, Walser Severin, Rai Arpan Kumar, Fujita Keisuke, Pelkmans Lucas
Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
Systems Biology PhD program, Life Science Zurich Graduate School, University of Zurich, Zurich, Switzerland.
Nat Commun. 2025 Jan 4;16(1):390. doi: 10.1038/s41467-024-55469-3.
Nuclear speckles are membraneless organelles that associate with active transcription sites and participate in post-transcriptional mRNA processing. During the cell cycle, nuclear speckles dissolve following phosphorylation of their protein components. Here, we identify the PP1 family as the phosphatases that counteract kinase-mediated dissolution. PP1 overexpression increases speckle cohesion and leads to retention of mRNA within speckles and the nucleus. Using APEX2 proximity labeling combined with RNA-sequencing, we characterize the recruitment of specific RNAs. We find that many transcripts are preferentially enriched within nuclear speckles compared to the nucleoplasm, particularly chromatin- and nucleus-associated transcripts. While total polyadenylated RNA retention increases with nuclear speckle cohesion, the ratios of most mRNA species to each other are constant, indicating non-selective retention. We further find that cellular responses to heat shock, oxidative stress, and hypoxia include changes to the phosphorylation and cohesion of nuclear speckles and to mRNA retention. Our results demonstrate that tuning the material properties of nuclear speckles provides a mechanism for the acute control of mRNA localization.
核斑点是无膜细胞器，与活跃的转录位点相关联并参与转录后mRNA加工。在细胞周期中，核斑点在其蛋白质成分磷酸化后溶解。在这里，我们确定PP1家族为对抗激酶介导的溶解作用的磷酸酶。PP1的过表达增加了斑点的凝聚性，并导致mRNA在斑点和细胞核内滞留。使用APEX2邻近标记结合RNA测序，我们对特定RNA的募集进行了表征。我们发现，与核质相比，许多转录本在核斑点中优先富集，特别是与染色质和细胞核相关的转录本。虽然总的多聚腺苷酸化RNA滞留随着核斑点凝聚性的增加而增加，但大多数mRNA种类之间的比例是恒定的，表明是无选择性的滞留。我们进一步发现，细胞对热休克、氧化应激和缺氧的反应包括核斑点的磷酸化和凝聚性以及mRNA滞留的变化。我们的结果表明，调节核斑点的物质特性为mRNA定位的急性控制提供了一种机制。
