TATA-BINDING PROTEIN AND ASSOCIATED FACTORS IN POLYMERASE-II AND POLYMERASE-III TRANSCRIPTION

Transcription by RNA polymerase I (pol I), pol II, and pol III require s the TATA-binding protein (TBP). This protein functions in associatio n with distinct TBP-associated factors (TAFs) which may specify the na ture of the polymerase selected for initiation at a promoter site. In the pol III transcription system, the TBP-TAF complex is a component o f the TFIIIB factor. This factor has been resolved into a TBP-TAF comp lex and another component, both of which are required for reconstituti on of transcription by pol III. Neither the TBP-TAF complexes B-TFIID and D-TFIID, which were previously characterized as active for pol II transcription, nor TBP alone can complement pol III transcription reac tions that are dependent upon the TBP-TAF subcomponent of TFIIIB. Surp risingly, the TBP-TAF subcomponent of TFIIIB is active in reconstituti on of pol II transcription.