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TopicPage for Stalled RNAP-Promoter Complexes of Escherichia coli K-12

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Transcription Initiation         


Promoter-proximal complexes of RNA polymerase and DNA were identified using in vivo KMnO(4) mapping (Hatoum, 2008). 118 candidate promoters were screened, 34 active promoters were identified, and seven promoters, lacZp, tnaAp, cspAp, cspDp, rplKp, rpsAp and rpsUp were found to have stalled RNAP polymerases attached in vivo.


After open complex formation, stable non-elongating complexes of RNAP and DNA can be formed by two distinct processes. A failure to complete promoter clearance can lead to an RNAP trapped in an intermediate stage of the final promoter escape phase of transcription intitiation after open complex formation causing abortive initiations and restarts. Alternatively, a second -10 sequence immediately downstream of the promoter can cause RNAP to pause and backtrack, stabilized by elongation phase core enzyme DNA contacts. Both types of stable complexes were eliminated by the RpoDL402F mutation and enhanced in a greA mutant.
The candidate, active, and complexed promoters are described in subtopics.

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