Coordinated Control of rRNA Processing by RNA Polymerase I.

Ribosomal RNA (rRNA) is co- and post-transcriptionally processed into active ribosomes. This process is dynamically regulated by direct covalent modifications of the polymerase that synthesizes the rRNA, RNA polymerase I (Pol I), and by interactions with cofactors that influence initiation, elongation, and termination activities of Pol I. The rate of transcription elongation by Pol I directly influences processing of nascent rRNA, and changes in Pol I transcription rate result in alternative rRNA processing events that lead to cellular signaling alterations and stress. It is clear that in divergent species, there exists robust organization of nascent rRNA processing events during transcription elongation. This review evaluates the current state of our understanding of the complex relationship between transcription elongation and rRNA processing. Transcription elongation rate by RNA polymerase I dynamically controls ribosome biogenesis directly. Conservation of transcription factors and processing pathways suggests that dynamic regulation of Pol I is conserved from lower to higher eukaryotes. Dysregulation of transcription by Pol I and pre-rRNA processing is observed in several diseases, resulting in altered cell growth and signaling pathways. Emerging technologies both in vivo and in vitro will allow for a better understanding of the dynamic nature of ribosome biogenesis. [ABSTRACT FROM AUTHOR]