In Escherichia coli, the holoenzyme form of RNA polymerase recognises promoters, whereas the core enzyme extends an RNA chain but cannot initiate at specific sites. The subunit conferring promoter specificity contacts two conserved upstream sequence elements. These elements are located at:

• A +1 and +20 downstream of the transcription start site
• B -25 and +1 relative to the transcription start site
• C -70 and -40 relative to the transcription start site
• D -35 and -10 relative to the transcription start site ✓

Explanation

Sigma factor positions the core polymerase at promoters containing the conserved -35 box (consensus TTGACA) and the Pribnow box at -10 (consensus TATAAT), separated by roughly 17 base pairs. The -25 TATA element is the eukaryotic core promoter bound by TBP through TFIID, not a prokaryotic feature. Downstream sequences are not involved in initiation specificity.

Reference: Lewin's Genes XII, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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