What enzyme is responsible for binding promoters to initiate transcription?

RNA polymerase is the enzyme responsible for binding to promoters to initiate transcription. Promoters are specific sequences of DNA located at the start of genes, and they serve as the binding sites for RNA polymerase. When RNA polymerase attaches to a promoter, it unwinds the DNA and begins synthesizing RNA from the DNA template in the direction of transcription. This initiation of transcription is a crucial step in gene expression, as it marks the beginning of the process where genetic information is converted into RNA.

In contrast, DNA polymerase is primarily involved in DNA replication, not transcription. Ligase plays a role in joining fragments of DNA during replication and repair processes, while helicase is responsible for unwinding the DNA double helix ahead of the replication fork and is not directly involved in the transcription process itself. Thus, RNA polymerase is uniquely suited for this function, making it the correct answer.