title: Probing Zn2+-binding effects on the zinc-ribbon domain of human general transcription factor TFIIB.
abstract: The general transcription factor, TFIIB, plays an important role in the assembly of the pre-initiation complex. The N-terminal domain (NTD) of TFIIB contains a zinc-ribbon motif, which is responsible for the recruitment of RNA polymerase II and TFIIF to the core promoter region. Although zinc-ribbon motif structures of eukaryotic and archaeal TFIIBs have been reported previously, the structural role of Zn2 binding to TFIIB remains to be determined. In the present paper, we report NMR and biochemical studies of human TFIIB NTD, which characterize the structure and dynamics of the TFIIB Zn2-binding domain in both Zn2-bound and -free states. The NMR data show that, whereas the backbone fold of NTD is pre-formed in the apo state, Zn2 binding reduces backbone mobility in the b-turn (Arg28-Gly30), induces enhanced structural rigidity of the charged-cluster domain in the central linker region of TFIIB and appends a positive surface charge within the Zn2-binding site. V8 protease-sensitivity assays of full-length TFIIB support the Zn2-dependent structural changes. These structural effects of Zn2 binding on TFIIB may have a critical role in interactions with its binding partners, such as the Rpb1 subunit of RNA polymerase II.
authors.affiliation: Division of Molecular and Structural Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
authors.forename: Mahua
authors.initials: M
authors.lastname: Ghosh
authors.forename: Laura M
authors.initials: LM
authors.lastname: Elsby
authors.forename: Tapas K
authors.initials: TK
authors.lastname: Mal
authors.forename: Jane M
authors.initials: JM
authors.lastname: Gooding
authors.forename: Stefan G E
authors.initials: SG
authors.lastname: Roberts
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Ikura
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002413:Cations, Divalent / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D035581:Transcription Factor TFIIB / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D035581:Transcription Factor TFIIB; D010450:Endopeptidases; D015032:Zinc