Video narration
How does RNA polymerase know where to start a gene, if it cannot simply find one and begin? Think of starting a group project: first, you need a marked starting point and the right team. On DNA, that starting region is the promoter. It marks where transcription should begin. General transcription factors recognize the promoter and assemble the launch team. Other regulatory proteins can help, and together they recruit and position RNA polymerase II at the gene's start site. But polymerase's arrival is not the start. TFIIH then helps open the local DNA, exposing the template strand, and activates polymerase II. Only after that preparation can polymerase join the first RNA building blocks into bonds. It makes a short beginning, then escapes the promoter and moves into transcription. It starts with a promoter, recruited factors, opened DNA, and an activated polymerase II-not polymerase arriving alone.