Name the two main promoter elements in bacterial transcription and what they recruit.

• A. The -50 and -25 promoter boxes; they recruit the RNA polymerase core enzyme.
• B. The TATA box and Initiator; they recruit the transcription factors.
• C. The -35 and -10 promoter boxes; they recruit the RNA polymerase holoenzyme via the sigma factor.
• D. The GC box and CAAT box; they recruit RNA polymerase.

Answer: (C)

In bacteria, promoter recognition is driven by sigma factor binding to promoter sequences. The two main promoter boxes are located about 35 and 10 bases upstream of the transcription start site. These sequences are specifically recognized by the sigma factor, which is part of the RNA polymerase holoenzyme. When sigma binds these boxes, it positions the core enzyme at the promoter, helps melt the DNA to form the open complex, and starts RNA synthesis. This is distinct from eukaryotic promoter elements like the TATA box, Initiator, GC box, and CAAT box, which recruit transcription factors rather than the bacterial sigma factor and holoenzyme. The holoenzyme’s sigma factor is essential for promoter specificity, so the promoter boxes at -35 and -10 recruit the RNA polymerase holoenzyme to initiate transcription.