Guidi et al., J Biol Chem 2004
:
Mediator , a global transcriptional co-activator, dramatically enhances the phosphorylation of the CTD of RNA pol II by holo-TFIIH in vitro ... Using purified proteins we have determined that the subunits of TFIIK are sufficient for Mediator to enhance Kin28 CTD kinase activity and that Mediator enhances phosphorylation of a glutathione S-transferase-CTD fusion protein, despite the absence of multiple Mediator and/or TFIIH interactions with polymerase
Aristizabal et al., PLoS Genet 2013
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Here, loss of CDK8 suppressed the reduced mRNA expression and RNAPII occupancy levels of CTD truncation mutants
Gold et al., Nucleic Acids Res 1996
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Therefore, CDK8 is likely responsible for the E1A- and VP16 associated CTD kinase activity