| Protein protein interactions between human heat shock transcription factor 1 ( hHSF 1 ) and general transcription factors TFIIA gamma , TFIIB , TBP , TAF ( 2 ) 32 , and TAF ( 2 ) 55 and positive coactivator PC 4 were characterized in order to identify potential targets of contact in the transcriptional preinitiation complex . ^^^ TATA binding protein ( TBP ) and transcription factor IIB ( TFIIB ) were identified as major targets for HSF 1 transcriptional activation domains AD 1 and AD 2 based on in vitro interaction assays . ^^^ Assays based on transcriptional interference confirmed predictions that both TBP and TFIIB can interact with HSF 1 activation domains in HeLa cells . ^^^ |