Which factor is required for RNA polymerase II to recognize promoters in eukaryotes?

Which factor is required for RNA polymerase II to recognize promoters in eukaryotes?

• A. RNA polymerase II itself
• B. Transcription factors
• C. Sigma factors
• D. Enhancers

Answer: (B)

In eukaryotes, promoter recognition by RNA polymerase II depends on transcription factors. Pol II does not have a built-in promoter–recognition subunit like bacterial sigma factors; instead, general transcription factors assemble at the promoter to form the preinitiation complex and recruit Pol II. The process starts with a factor like TFIID recognizing core promoter elements (for example, the TATA box) via TBP, which anchors the complex and brings in other factors such as TFIIA and TFIIB. These, in turn, recruit RNA Pol II together with TFIIF. TFIIH then helps unwind the DNA and phosphorylate the polymerase’s CTD to allow promoter escape into elongation. Enhancers can boost transcription by looping to the promoter and modulating activity, but they are not required for the initial recognition step. So the essential component responsible for recognizing promoters and assembling the transcription machinery is the set of transcription factors.

In eukaryotes, promoter recognition by RNA polymerase II depends on transcription factors. Pol II does not have a built-in promoter–recognition subunit like bacterial sigma factors; instead, general transcription factors assemble at the promoter to form the preinitiation complex and recruit Pol II. The process starts with a factor like TFIID recognizing core promoter elements (for example, the TATA box) via TBP, which anchors the complex and brings in other factors such as TFIIA and TFIIB. These, in turn, recruit RNA Pol II together with TFIIF. TFIIH then helps unwind the DNA and phosphorylate the polymerase’s CTD to allow promoter escape into elongation. Enhancers can boost transcription by looping to the promoter and modulating activity, but they are not required for the initial recognition step. So the essential component responsible for recognizing promoters and assembling the transcription machinery is the set of transcription factors.