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. Author manuscript; available in PMC: 2022 Apr 1.
Published in final edited form as: Trends Biochem Sci. 2022 Feb 19;47(4):314–327. doi: 10.1016/j.tibs.2022.01.002

Figure 3. Schematic of the RNA polymerase II Pre-initiation complex (PIC).

Figure 3.

PIC structure is based upon cryoEM data from human complexes [41-43]. Each red X denotes Mediator kinase phosphorylation sites (MED14, MED26, TAF10, POLR2M) and their approximate location in the PIC. Because PIC structure is dynamic, specific sites may be phosphorylated only during select transcriptional stages (e.g. pol II pause release). The TFIIH-associated CDK-activating kinase module (CAK) binds Mediator at a similar site compared with the Mediator kinase module (MKM). This site would position the MKM downstream of the transcription start site, which may be important for MKM-dependent regulation of pol II pause release or elongation. IIA: TFIIA, IIB: TFIIB, IID, TFIID, IIE, TFIIE, IIF: TFIIF, IIH: TFIIH, TBP: TATA binding protein, CTD: C-terminal domain, CAK: CDK activating kinase module (CDK7, CCNH, MNAT1), part of TFIIH.