Lineage-specific transcription factor CEBPA accelerates RNA Polymerase I dynamics

Acute degradation of the myeloid transcription factor CEBPA rapidly reduces nascent rRNA synthesis by impairing RNA polymerase I promoter escape and altering Pol I dynamics on rDNA repeats.

• Why it matters: Cell-type-specific control of rRNA transcription is poorly understood, and whether lineage-specific transcription factors modulate Pol I activity has remained controversial.
• What they did: CEBPA was acutely degraded, then nascent rRNA synthesis, active rDNA proportions, and MYC/mTOR activity were assessed; time-resolved ChIP-seq and live-cell single-molecule tracking of Pol I and RRN3 mapped changes along rDNA.
• The result: CEBPA loss reduces Pol I promoter escape, increases Pol I accumulation along the gene body, and increases Pol I stability in the fibrillar center, with reduced Pol I-RRN3 loading and reduced TOP1 and TOP2A occupancy, implicating impaired DNA supercoiling resolution.