Table 1.
General class II transcription initiation factors from human cells
| Factor | Subunits, kDa | (no.) | Function | |
|---|---|---|---|---|
| TFIID | /TBP | 38 | (1) | Binds to TATA, promotes TFIIB binding |
| \TAFs* | 15–250 | (12) | Regulatory functions (+ and −) | |
| TFIIB | 35 | (1) | Promotes TFIIF–pol II binding | |
| TFIIF | 30, 74 | (2) | Targets pol II to promoter | |
| RNA pol II | 10–220 | (12) | Catalytic function | |
| TFIIE | 34, 57 | (2) | Stimulates TFIIH kinase and ATPase activities | |
| TFIIH | 35–89 | (9) | Helicase, ATPase, CTD kinase activities | |
| All class II GTFs | > 2 MDa | (>42) |
Function and subunit composition of the human class II general initiation factors. The factor denoted with an asterisk is not absolutely required for in vitro basal or core promoter-dependent pol II transcription initiation. TBP, TATA box-binding protein; TAF, TBP-associated factor; GTF, general transcription factor.