- The nucleolus is the most prominent membrane-less subnuclear structure found in all eukaryotic cells during interphase, although it disappears during mitosis.
- Traditionally, the nucleolus has been associated with ribosome biogenesis, but it also plays a crucial role in various cellular processes including apoptosis, cell-cycle regulation, stress sensing, telomerase production.
- The nucleolus consists of three major compartments: the fibrillar center (FC), the dense fibrillar component (DFC), and the granular component (GC).
- Transcription of ribosomal genes (rDNA) by RNA polymerase I occurs in the fibrillar center (FC), while the processing of pre-ribosomal RNA (pre-rRNA) transcripts takes place in the dense fibrillar component (DFC). In the granular component (GC), processed tRNA is assembled into functional 18S, 5.8S, and 28S rRNAs.
