Minimal Machinery of RNA Polymerase Holoenzyme Sufficient for Promoter Melting

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Science  27 Feb 2004:
Vol. 303, Issue 5662, pp. 1382-1384
DOI: 10.1126/science.1092462

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We determined the minimal portion of Escherichia coli RNA polymerase (RNAP) holoenzyme able to accomplish promoter melting, the crucial step in transcription initiation that provides RNAP access to the template strand. Upon duplex DNA binding, the N terminus of the β′ subunit (amino acids 1 to 314) and amino acids 94 to 507 of the σ subunit, together comprising less than one-fifth of RNAP holoenzyme, were able to melt an extended –10 promoter in a reaction remarkably similar to that of authentic holoenzyme. Our results support the model that capture of nontemplate bases extruded from the DNA helix underlies the melting process.

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