rRNA Gene Transcription Initiation Complex - Molecular Mechanism #238263 (License: Personal Use)

This schematic illustrates the stepwise assembly of the RNA Polymerase I (Pol I) pre-initiation complex on the ribosomal RNA (rRNA) gene promoter. Upstream Binding Factor (UBF) binds both the upstream promoter element (-186) and core promoter element (-50 to -31), facilitating recruitment of Selectivity Factor 1 (SL1) and the Pol I-PAF53 subcomplex near the transcription start site (+20). The diagram emphasizes spatial organization and protein-DNA interactions essential for ribosome biogenesis.

Used in molecular biology education, research presentations, and genomics resources to explain Pol I transcription regulation; targets students, researchers, and clinicians interested in gene expression or nucleolar function.