Extended Data Fig. 1: Transcription termination mechanisms commonly employed in Bacteria, Eukarya and Archaea.

Intrinsic transcription termination in Bacteria (a), Archaea (b), and for eukaryotic Pol III (c) results in release of the entire 5′-triphosphate-containing RNA transcript following transcription through a region of dyad-symmetry encoding an RNA hairpin immediately proceeded a T-rich non-template strand sequence (Bacteria)⁶⁴ or T-rich non-template strand sequences (Archaea and eukaryotic Pol III)^{20,32,65,66,67,68,69}. d, g, Factor-mediated bacterial transcription termination⁶⁴, driven by rho or Mfd, also directs release of the entire nascent transcript and results in collapse of the TEC and recycling of RNAP. Rho-mediated termination is aided by NusG (Spt5 in Eukarya and Archaea)^{34,36,70,71,72}. e, Release of the majority of the nascent transcript cannot be considered a bona fide termination event in-of-itself. RNA processing events, such as the endonucleolytic cleavage of the nascent RNA within eukaryotic Pol II TECs by the cleavage and polyadenylation factor complex (CPSF)^{16,25,50,57,61} yield a 5′-fragment that is often further processed – typically by the addition of a 3′-polyA tail for many Pol II transcripts – but also a 3′-fragment that is encapsulated within a still-stable TEC;^28,60 the combined activities of CPSF and Xrn2 are necessary for normal termination patterns in Eukarya^59,60,73. f, FttA can cleave the nascent transcript and terminate the archaeal transcription apparatus. g, h, Both bacterial Mfd and archaeal Eta can disrupt stalled TECs and release full-length transcripts by rewinding the transcription bubble.