Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.
Development. 2023 Dec 15;150(24). doi: 10.1242/dev.202284. Epub 2023 Dec 11.
RNA silencing pathways are complex, highly conserved, and perform crucial regulatory roles. In Caenorhabditis elegans germlines, RNA surveillance occurs through a series of perinuclear germ granule compartments - P granules, Z granules, SIMR foci, and Mutator foci - multiple of which form via phase separation. Although the functions of individual germ granule proteins have been extensively studied, the relationships between germ granule compartments (collectively, 'nuage') are less understood. We find that key germ granule proteins assemble into separate but adjacent condensates, and that boundaries between germ granule compartments re-establish after perturbation. We discover a toroidal P granule morphology, which encircles the other germ granule compartments in a consistent exterior-to-interior spatial organization, providing broad implications for the trajectory of an RNA as it exits the nucleus. Moreover, we quantify the stoichiometric relationships between germ granule compartments and RNA to reveal discrete populations of nuage that assemble in a hierarchical manner and differentially associate with RNAi-targeted transcripts, possibly suggesting functional differences between nuage configurations. Our work creates a more accurate model of C. elegans nuage and informs the conceptualization of RNA silencing through the germ granule compartments.
RNA 沉默途径复杂、高度保守,发挥着关键的调节作用。在秀丽隐杆线虫的生殖系中,RNA 监测通过一系列核周生殖质颗粒隔室——P 颗粒、Z 颗粒、SIMR 焦点和 Mutator 焦点——发生,其中多个隔室通过相分离形成。尽管单个生殖质颗粒蛋白的功能已被广泛研究,但生殖质颗粒隔室(统称为“核质”)之间的关系还不太清楚。我们发现关键的生殖质颗粒蛋白组装成单独但相邻的凝聚体,并且在扰动后生殖质颗粒隔室之间的边界重新建立。我们发现了一种环形 P 颗粒形态,它以一致的外到内的空间组织环绕其他生殖质颗粒隔室,这为 RNA 从核内输出的轨迹提供了广泛的影响。此外,我们量化了生殖质颗粒隔室和 RNA 之间的化学计量关系,揭示了核质以分层方式组装的离散群体,并与 RNAi 靶向转录本不同程度地相关,这可能表明核质构型之间存在功能差异。我们的工作为秀丽隐杆线虫的核质创建了一个更准确的模型,并通过生殖质颗粒隔室为 RNA 沉默的概念化提供了信息。