“…Rho is a ring-shaped hexameric RNA helicase that travels with elongating RNAP (Epshtein et al, 2010; Nudler and Gottesman, 2002; Skordalakes and Berger, 2003). To terminate transcription Rho binds to relatively unstructured nascent RNA ( rut sites), categorized as ≈ 80 nt long regions with high cytidine/low guanine content (Boudvillain et al, 2013; Ciampi, 2006; Epshtein et al, 2010; Hart and Roberts, 1991; Peters et al, 2011; Salstrom et al, 1979). For iRAPs the C-content median value is 32.8%, whereas G-content median value is 15.4% (Figure S2D and E), suggesting that they can in principle facilitate Rho loading.…”