rRNA intermediates coordinate the formation of nucleolar vacuoles in C. elegans

• Published in: Cell reports (Cambridge) Vol. 42; no. 8; p. 112915
• Main Authors: Xu, Demin, Chen, Xiangyang, Kuang, Yan, Hong, Minjie, Xu, Ting, Wang, Ke, Huang, Xinya, Fu, Chuanhai, Ruan, Ke, Zhu, Chengming, Feng, Xuezhu, Guang, Shouhong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29.08.2023; Elsevier
• Subjects: CP: Cell biology; CP: Molecular biology; nucleolus; phase transition; reshaping; ring; RNAPI; rRNA; vacuole; vacuole; CP: Cell biology; ring; rRNA; nucleolus; CP: Molecular biology; RNAPI; reshaping; phase transition
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2023.112915

The nucleolus is the most prominent membraneless organelle within the nucleus. How the nucleolar structure is regulated is poorly understood. Here, we identified two types of nucleoli in C. elegans. Type I nucleoli are spherical and do not have visible nucleolar vacuoles (NoVs), and rRNA transcription and processing factors are evenly distributed throughout the nucleolus. Type II nucleoli contain vacuoles, and rRNA transcription and processing factors exclusively accumulate in the periphery rim. The NoV contains nucleoplasmic proteins and is capable of exchanging contents with the nucleoplasm. The high-order structure of the nucleolus is dynamically regulated in C. elegans. Faithful rRNA processing is important to prohibit NoVs. The depletion of 27SA2 rRNA processing factors resulted in NoV formation. The inhibition of RNA polymerase I (RNAPI) transcription and depletion of two conserved nucleolar factors, nucleolin and fibrillarin, prohibits the formation of NoVs. This finding provides a mechanism to coordinate structure maintenance and gene expression. [Display omitted] •The appearance of nucleolar vacuole is dynamic in C. elegans•Nucleolar vacuoles contain nucleoplasmic proteins•The accumulation of 27SA2 rRNAs promotes nucleolar vacuole formation•FIB-1 and NUCL-1 are required for nucleolar vacuole formation Xu et al. found that the nucleolar vacuole (NoV) contains nucleoplasmic proteins and is capable of exchanging its contents with nucleoplasm. The formation of the NoV is orchestrated by rRNA transcription, processing, and maturation.