 processing shapes the internal architecture of the nucleolus, the cell’s most prominent nuclear structure. The study, recently published in Nature, sheds light on the intricate choreography that allows the nucleolus to carry out its central role in producing ribosomes.){kind=link}
Researchers have mapped how ribosomal RNA (rRNA) processing shapes the internal architecture of the nucleolus, the cell’s most prominent nuclear structure. The study, recently published in Nature, sheds light on the intricate choreography that allows the nucleolus to carry out its central role in producing ribosomes.
Though the nucleolus has been recognized since the 19th century, its complex, layered organization has remained poorly understood. At its core, the nucleolus is a membraneless structure composed of distinct liquid-like phases, where precursor rRNAs are transcribed, processed, and assembled into the small and large subunits of ribosomes (SSU and LSU). This latest research reveals that rRNA itself not only undergoes transformation in the nucleolus, but actively dictates how its surrounding environment is built.
Using a combination of high-resolution sequencing and advanced imaging, the researchers traced the maturation of rRNA within the nucleolus, discovering that the various steps of rRNA processing occur in spatially segregated phases. As pre-rRNA matures, it physically moves outward through these layers, a process that appears to be tightly regulated and structurally encoded.
To further probe this phenomenon, the team engineered synthetic nucleoli within human cells using custom-designed DNA plasmids. These artificial systems allowed them to manipulate rRNA processing and observe how specific defects influence nucleolar organization. They found that disruptions in SSU processing led to a dramatic reordering of the nucleolus, effectively flipping its structure inside-out and halting rRNA flow. Meanwhile, LSU precursors were shown to be essential for maintaining the outermost layer of the nucleolus.
Their findings highlight a novel role for rRNA, it not only serves as the raw material for ribosome assembly but also acts as a structural scaffold that organizes the nucleolus itself. The study suggests that the nucleolus operates like a biochemical assembly line, with its layered architecture functioning as a quality control system to prevent the premature release of improperly processed ribosomal components.