Fig. 7
From: The transcript cleavage factor paralogue TFS4 is a potent RNA polymerase inhibitor
Global regulation of SsoRNAP transcription cycle by TFS1 and TFS4. a Structural homology model of the Sso RNAP-TFS4 transcription elongation complex in which TFS4 is bound to RNAP akin to the A12 subunit to RNAPI. TFS4 is shown as surface representation in orange. b Surface representation of the yeast RNAPII–TFIIS complex highlighting RPB9 and TFIIS in orange and red, respectively. c A schematic representation of SsoRNAP transcription cycle. TFS1 stimulates productive transcription and rescues backtracked complexes by stimulating RNA cleavage by RNAP. In contrast, TFS4 inhibits transcription initiation by a two-fold mechanism. TFS4 (i) destabilises pre-initiation complexes (PICs) likely by an allosteric mechanism and (ii) interferes with catalysis by competing with substrate NTP binding. The basal factor TFEα/β stabilises the PIC and counteracts the inhibitory effect of TFS4, possibly by allosteric competition. During the elongation phase of transcription, TFS4 inhibits transcription by destabilising the RNAP–DNA–RNA complex and inhibiting catalysis
