Where does the assembly of transcription factors begin relative to the transcription start site?

Where does the assembly of transcription factors begin relative to the transcription start site?

• A. downstream from the transcription start site
• B. within the coding region
• C. at the terminator
• D. upstream from the transcription start site

Answer: (D)

Transcription factors assemble at the promoter region, which sits upstream (5' side) of the transcription start site. This upstream area contains promoter elements like the TATA box that help recruit general transcription factors and RNA polymerase II to form the pre-initiation complex. The polymerase is positioned to begin transcription at the correct base right after the promoter, so initiation happens downstream from this assembly. If assembly occurred downstream, in the coding region, or at the terminator, transcription wouldn’t start at the proper site. Thus, the assembly begins upstream from the transcription start site.

Transcription factors assemble at the promoter region, which sits upstream (5' side) of the transcription start site. This upstream area contains promoter elements like the TATA box that help recruit general transcription factors and RNA polymerase II to form the pre-initiation complex. The polymerase is positioned to begin transcription at the correct base right after the promoter, so initiation happens downstream from this assembly. If assembly occurred downstream, in the coding region, or at the terminator, transcription wouldn’t start at the proper site. Thus, the assembly begins upstream from the transcription start site.