Skip to main content
. Author manuscript; available in PMC: 2026 Feb 4.
Published in final edited form as: Cell Rep. 2025 Feb 24;44(3):115325. doi: 10.1016/j.celrep.2025.115325

Figure 1. RNAPI convoys are torsionally entrained on spinning DNA.

Figure 1

(A) Schematic of the 35S pre-rRNA.

(B) Image and schematics of the rDNA with RNAPI and nascent pre-ribosomes.

(C) Distribution of RNAPI CRAC reads along the rDNA, highlighting the peak at the 3′ end of the 35S pre-rRNA. Rpa190-HTP CRAC data re-processed from Turowski et al.7 Data are represented as median, 25%–75% quantile range, and minimum-maximum range (n = 6).

(D) Cartoon of the modeled RNAPI elongation rate along the rDNA. Top: multiple RNAPI molecules are torsionally entrained on the DNA, which is spinning rapidly (~230 rpm) during transcription elongation. Topoisomerase 1 (Top1) sites flanking the transcription unit release DNA torsion by introducing single-strand nicks in DNA.8,9,10 Center: cartoon of implementation of the low-entrainment region (LER): initial ability of RNAP to spin at the beginning of the transcription unit. Bottom: a consequence of the LER is a progressive increase of RNAP velocity at the beginning of the transcription unit.

(E) Schematic showing processing sites within the 3′ ETS: the B2 site at the very 3′ end of 25S rRNA, two B0 sites that are cleaved together across a stem structure by the RNase III homolog Rnt1, termination sites T1 and T2, and the binding site of the roadblock terminator Nsi1.

(F) Cartoon illustrating Rat1-Rai1 torpedo termination of RNAPI transcription.