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Structural Basis of Transcription Initiation

Science  18 Oct 2012:
pp.
DOI: 10.1126/science.1227786

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Abstract

During transcription initiation, RNA polymerase (RNAP) binds and unwinds promoter DNA to form an RNAP-promoter open complex. We have determined crystal structures at 2.9 and 3.0 Å resolution of functional transcription initiation complexes comprising Thermus thermophilus RNA polymerase, σA, and a promoter DNA fragment corresponding to the transcription bubble and downstream dsDNA of the RNAP-promoter open complex. The structures show that σ recognizes the –10 element and discriminator element through interactions that include the unstacking and insertion into pockets of three DNA bases, and that RNAP recognizes the –4/+2 region through interactions that include the unstacking and insertion into a pocket of the +2 base. The structures further show that interactions between σ and template-strand ssDNA preorganize template-strand ssDNA to engage the RNAP active center.

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