The structural basis for the oriented assembly of a TBP/TFB/promoter complex

Recently the definition of the metazoan RNA polymerase II and archaeal core promoters has been expanded to include a region immediately upstream of th e TATA box called the B recognition element (BRE), so named because eukarya l transcription factor TFIIB and its archaeal orthologue TFB interact with the element in a sequence-specific manner. Here we present the 2.4-Angstrom crystal structure of archaeal TBP and the C-terminal core of TFB (TFBc) in a complex with an extended TATA-box-containing promoter that provides a de tailed picture of the stereospecific interactions between the BRE and a hel ix-turn-helix motif in the C-terminal cyclin repeat of TFBc. This interacti on is important in determining the level of basal transcription and explici tly defines the direction of transcription.