Figure 1. FIGURE 1: Compartmentalization of ribosome biogenesis in the nucleoli.

The rRNAs are transcribed by the RNA polymerase I as a single precursor (47S) at the interface between the FC and the DFC. The mature rRNAs are produced in the DFC and assembled into large and small ribosomal subunits by binding to the ribosomal proteins (RP) coming from the cytoplasm and the 5S (produced in the nucleoplasm) in the GC. Interaction of rRNA and AluRNAs with proteins leads to the formation of nucleoli through liquid-liquid phase separation. Under conditions of stress, IGS RNAs and PAPAs are upregulated thus leading to nucleolar remodeling and rRNA transcriptional silencing respectively. Nucleolar remodeling results in the formation of DC (Detention Centers). SLERT and SAMMSON regulate rRNA transcription and processing respectively.