The central component of a transcription initiation complex is RNA polymerase. Transcription initiation complex refers to the complex of proteins that is required to initiate the transcription of DNA to RNA. The RNA polymerase enzyme is responsible for the synthesis of RNA from the DNA template. It recognizes the promoter sequence of DNA and initiates the process of transcription by unwinding the DNA double helix and beginning the synthesis of RNA. Other components of the transcription initiation complex include transcription factors that bind to the promoter region of DNA and help to recruit RNA polymerase to the correct site of transcription initiation. Once the transcription initiation complex is assembled, RNA polymerase begins transcription and continues until it reaches the end of the gene or is terminated by other regulatory factors.