During the initiation step of transcription, what binds to a promoter?

During the initiation step of transcription, RNA polymerase binds to a promoter region of the DNA. The promoter is a specific sequence that signals the start point for transcription and ensures that RNA polymerase attaches to the correct place on the DNA.

Once RNA polymerase is bound, it unwinds the DNA strands and begins synthesizing a complementary RNA strand, based on the sequence of the DNA template. The role of RNA polymerase is crucial, as it facilitates the formation of the mRNA transcript directly from the DNA.

While transcription factors also play a significant role in initiating transcription, as they help recruit RNA polymerase to the promoter, it is RNA polymerase that directly binds to the promoter to start the transcription process. Thus, the primary factor in this specific context is RNA polymerase.