nucleolus

The nucleolus is the dense globular mass of material within the nucleus. As the cell grows, one or more nucleoli may appear. Nucleoli are sites where the RNA subunits and ribosomes are assembled. These subunits are then shipped out of the nucleus into the cytoplasm where proteins can be synthesized and the functional ribosomes can attach to the rough ER.

Function

 assembling ribosomal subunits is well established
 processing and modification of preribosomal RNA
 nuclear export
 sequestering regulatory molecules
 modifying small RNAs
 assembling ribonucleoprotein (RNP)
 controlling aging

References

 Thiry M, Lafontaine DL. Birth of a nucleolus: the evolution of nucleolar compartments. Trends Cell Biol. 2005 Apr;15(4):194-9. PMID: 15817375

 Olson MO, Dundr M, Szebeni A. The nucleolus: an old factory with unexpected capabilities. Trends Cell Biol. 2000 May;10(5):189-96. PMID: 10754561