What is the role of RNA polymerase in transcription?

RNA polymerase is the main enzyme involved in transcription.

Transcription takes place in three main stages. RNA polymerase plays a key role in all three of these stages.

Initiation is the first step in transcription. In this step, RNA polymerase (RNAP) binds to the promoter sequence of DNA found near the beginning of a gene. After binding, RNAP unzips or separates the two DNA strands, creating a single-stranded template that’s necessary for transcription.

Elongation is the second step. In this step, RNA polymerase reads the template strand of DNA one base at a time and builds an RNA transcript molecule from complementary nucleotides, creating a chain that develops from 5' to 3'. This RNA transcript carries the same information as the non-template DNA strand with one difference – instead of thymine (T) it contains the base uracil (U).

Termination is the third and last step in transcription. In this step the completed RNA transcript and the RNA polymerase are separated. This happens after RNA polymerase encounters terminator sequences or signals that indicate the RNA transcript is complete. The RNA polymerase then releases the completed RNA transcript, which marks the end of transcription for that template of DNA.