Journal:Science:1

spinqualitylabelsall models Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural basis of transcription activation Yu Feng, Yu Zhang, Richard H. Ebright Molecular Tour Class II transcription activators function by binding to a DNA site overlapping a core promoter and stimulating isomerization of an initial RNA polymerase (RNAP)–promoter closed complex into a catalytically competent RNAP-promoter open complex. Here, we report a 4.4 angstrom crystal structure of an intact bacterial class II transcription activation complex. The structure comprises Thermus thermophilus transcription activator protein TTHB099 (TAP) [homolog of Escherichia coli catabolite activator protein (CAP)], T. thermophilus RNAP σA holoenzyme, a class II TAP-dependent promoter, and a ribotetranucleotide primer. The structure reveals the interactions between RNAP holoenzyme and DNA responsible for transcription initiation and reveals the interactions between TAP and RNAP holoenzyme responsible for transcription activation. The structure indicates that TAP stimulates isomerization through simple, adhesive, stabilizing protein-protein interactions with RNAP holoenzyme. To obtain a structure of TAP-RPo, we used a nucleic-acid scaffold corresponding to positions –57 to +15 (-54 to +11 shown) of a class II TAP-dependent promoter (positions numbered relative to transcription start site). Pink, nontemplate strand; red, template strand. The scaffold contained a consensus DNA site for TAP centered between positions –41 and –42 (TAP site: cyan, template strand; deeppink, nontemplate strand), a near-consensus extended –10 element (violet), a consensus –10 element (blue), a consensus discriminator element (royalblue), a consensus core recognition element, a 13-bp transcription bubble (maintained in the unwound state by having noncomplementary sequences on nontemplate and template strands), and UpCpGpA (in magenta). Protein-DNA interactions that mediate promoter recognition TAP site. TAP is in cyan, σ is in yellow. Pink, nontemplate strand; red, template strand. Interactions between σR4 and –35 region. Interactions between σR3 and extended –10 element (in violet). Interactions between σR2 consensus –10 element (in blue).

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