Which function does the sigma factor primarily provide in bacterial transcription?

Which function does the sigma factor primarily provide in bacterial transcription?

• A. Promoter recognition
• B. Catalysis of RNA synthesis
• C. Ribosome binding
• D. DNA replication initiation

Answer: (A)

Promoter recognition guides bacterial transcription. The sigma factor binds to the RNA polymerase core enzyme to form the holoenzyme, and its main job is to identify and bind promoter sequences upstream of genes. It recognizes conserved promoter elements, such as the -35 and -10 regions, which positions the polymerase at the correct start site, helps unwind the DNA to form the open complex, and enables the first nucleotides to be added. After transcription begins, the sigma factor is typically released, and elongation proceeds with the core enzyme. The other options don’t fit because catalysis of RNA synthesis is carried out by the core enzyme’s active site, ribosome binding is a step in translation, and DNA replication initiation involves different initiator proteins, not transcription initiation.

Promoter recognition guides bacterial transcription. The sigma factor binds to the RNA polymerase core enzyme to form the holoenzyme, and its main job is to identify and bind promoter sequences upstream of genes. It recognizes conserved promoter elements, such as the -35 and -10 regions, which positions the polymerase at the correct start site, helps unwind the DNA to form the open complex, and enables the first nucleotides to be added. After transcription begins, the sigma factor is typically released, and elongation proceeds with the core enzyme. The other options don’t fit because catalysis of RNA synthesis is carried out by the core enzyme’s active site, ribosome binding is a step in translation, and DNA replication initiation involves different initiator proteins, not transcription initiation.