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Structural basis of transcription activation

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Science  10 Jun 2016:
Vol. 352, Issue 6291, pp. 1330-1333
DOI: 10.1126/science.aaf4417

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Transcription activation all about timing

Regulating transcription by RNA polymerase (RNAP) is central to controlling gene expression. Transcription factors influence the activity of the RNAP. Feng et al. determined the crystal structure of a bacterial transcription activation complex. The transcription activator protein (TAP) converts the closed RNAP-promoter complex into an open complex through simple stabilizing protein-protein interactions with RNAP. The critical contacts did not go through the RNAP active center or the RNAP clamp. Instead, it seems that the timing of the interaction during transcription complex formation is critical for activation.

Science, this issue p. 1330

Abstract

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.

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