prerRNA

prerRNA stands for precursor ribosomal RNA. It is an unprocessed RNA molecule that serves as a direct transcript of ribosomal RNA genes in eukaryotes. These prerRNAs are then processed through a series of biochemical steps to yield the mature ribosomal RNAs (rRNAs) that are essential components of ribosomes. Ribosomes are the cellular machinery responsible for protein synthesis.

In eukaryotes, the genes encoding the 18S, 5.8S, and 25S (or 28S in some species) rRNAs are transcribed as a single, large precursor molecule, typically referred to as the 45S prerRNA. This large transcript is synthesized by RNA polymerase I in the nucleolus. Following transcription, the prerRNA undergoes extensive processing involving cleavage, base modification, and folding. This processing is carried out by a complex set of enzymes and small nucleolar ribonucleoproteins (snoRNPs).

The processing of prerRNA is a crucial step in ribosome biogenesis. It ensures the production of functional rRNA molecules of the correct size and structure. Errors in prerRNA processing can lead to defects in ribosome assembly and function, potentially causing various cellular abnormalities and diseases. The mature 18S, 5.8S, and 25S/28S rRNAs then associate with ribosomal proteins to form the small and large ribosomal subunits, which are subsequently exported to the cytoplasm for protein synthesis.