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Granular component sub-phases direct ribosome biogenesis in the nucleolus
Priyanka Dogra1, Mylene C Ferrolino1, Suparna Khatun1
1Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA.
Molecular Cell
|July 15, 2026
Summary
Researchers uncovered how nucleolar granular component (GC) biomolecules form distinct phases, facilitating ribosome subunit assembly. This reveals a mechanism for spatial heterogeneity and efficient ribosome production.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The nucleolus is crucial for ribosome biogenesis, with its granular component (GC) housing ribonucleoprotein particles involved in ribosomal subunit assembly.
- The spatial heterogeneity within the GC and its role in assembly remain unclear.
Purpose of the Study:
- To investigate the molecular basis of spatial heterogeneity in the nucleolar GC.
- To understand how this heterogeneity contributes to ribosome subunit assembly.
Main Methods:
- Super-resolution microscopy in DLD-1 cells.
- In vitro reconstitution assays using bacterial and human ribosomal RNA (rRNA).
Main Results:
- Key GC biomolecules (NPM1, SURF6, rRNA) show heterogeneous localization within GC sub-phases.
- In vitro, these biomolecules form multiphase condensates with a SURF6/rRNA core and NPM1 shell.
- SURF6-rRNA interaction weakens during subunit assembly, allowing NPM1 to extract subunits.
Conclusions:
- Established a mechanistic framework for GC heterogeneity based on multiphase condensates.
- Proposed an assembly-line mechanism for ribosome subunit efflux from the GC.
- Demonstrated how distinct GC sub-phases facilitate efficient ribosome subunit assembly.
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