Transcriptional activity of the TFIIA four-helix bundle in vivo

TFIIA contributes to transcription initiation by stabilizing the TBP-TATA i nteraction and by mediating the response to transcriptional activators and inhibitors. TFIIA contains a six-stranded P-sheet domain and a four-helix b undle. The p-domain makes functional contacts with DNA and TBP, The role of the four-helix bundle was investigated using a structure-based model of th is domain (called 4HB), 4HB adopts a highly stable, helical fold, consisten t with its structure in the context of TFIIA, Like TBP and other intact tra nscription factors, 4HB is able to activate transcription in vivo when arti ficially recruited to a promoter via a heterologous DNA-binding domain. Thu s, in addition to making important contacts with TBP and DNA via the p-doma in, TFIIA makes other specific, functional contacts with the transcriptiona l machinery via the four-helix bundle. (C) 2001 Wiley-Liss,Inc.