Image removed for copyright considerations Source: Figure 5 in Muratani M, Tansey WP. "How the ubiquitin-proteasome system controls transcription "Nat Rev Mol Cell Biol. 2003 Mar: 4(3): 192-201 The ubiquitin(Ub)-proteasome system regulates transcription at numerous levels. a I Interactions of an activator with the general transcriptional machinery (green) functions to b recruit ubiquitin igase( s) to the site of transcription and ubiquitylates many factors including the activator, rna polymerase ii (pol Ir and histones. c These ubiquitylation events in turn recruit the 26s proteasome, which d I simultaneously destroys the activator and promotes elongation of transcription by pol II. Importantly, this proposed mechanism limits uncontrolled transcription in two ways by destroying the activator at each cycle of promoter 'firing and by ensuring that interactions between pol II and the proteasome are made in an activator and promoter-dependent manner.Image removed for copyright considerations. Source: Figure 5 in Muratani M, Tansey WP. "How the ubiquitin-proteasome system controls transcription." Nat Rev Mol Cell Biol. 2003 Mar;4(3):192-201. The ubiquitin (Ub)–proteasome system regulates transcription at numerous levels. a | Interactions of an activator with the general transcriptional machinery (green) functions to b | recruit ubiquitin ligase(s) to the site of transcription and ubiquitylates many factors, including the activator, RNA polymerase II (pol II) and histones. c | These ubiquitylation events in turn recruit the 26S proteasome, which d | simultaneously destroys the activator and promotes elongation of transcription by pol II. Importantly, this proposed mechanism limits uncontrolled transcription in two ways — by destroying the activator at each cycle of promoter 'firing' and by ensuring that interactions between pol II and the proteasome are made in an activator- and promoter-dependent manner