The nucleolus is a highly dynamic membraneless organelle, where RNA-protein fluxes drive ribosome biogenesis. While ensemble methods and static imaging have revealed key principles of nucleolar organization, direct measurements of molecular kinetics in living cells remain limited. Here, I introduce a single-molecule tracking platform using the ultra-high resolution of MINFLUX nanoscopy to probe the dynamics of small nucleolar RNAs (snoRNAs) and nucleolar proteins at nanometer precision and millisecond temporal resolution. Preliminary measurements reveal heterogeneous motion modes within nucleolar subdomains, with distinct diffusion and transient confinement regimes that correlate with functional states. Perturbations of ribosome biogenesis further reshape these flux patterns, providing a window into the kinetic architecture of nucleolar assembly. This approach establishes a new paradigm for dissecting RNA-protein fluxes in living cells. By directly connecting single-molecule behavior to nucleolar function, this work lays the foundation for a quantitative kinetic framework of ribosome biogenesis in health and disease.
Sheng et al. (Sun,) studied this question.