Abstract
Abstract TFIIB is an essential component of the machinery that transcribes protein-coding genes. The three-dimensional structure of the human TFIIB core domain (TFIIB c ) has been determined using multidimensional heteronuclear magnetic resonance spectroscopy. The molecule consists of two direct repeats that adopt similar α-helical folds, conferring pseudo-twofold symmetry. An extensive, central basic surface including an amphipathic a helix is critical to the function of TFIIB as a bridge between the TBP-promoter complex and RNA polymerase II and associated general and regulatory transcription factors. Similarities between the TFIIB c and cyclin A folds indicate that elements of the eukaryotic cell cycle control apparatus evolved from more fundamental transcriptional control components, demonstrating a link between the transcription and cell cycle molecular machineries.
