These transcription factors are sequentially bind to TATA box DNA to form a pre initiation complex. At last when TFIIH get bind, It phosphorylates Pol II to initiate transcription in the presence of ATP which are described in Figure 28.11

Figure 28.11 : Sequential addition of Transcription factor

Mediator: For transcription activation mediator is required. Transcription  requires various activator proteins .Mediator is a protein complex which serves as bridge between co activator and enhancer, and between promoter and RNA polymerase.

TRANSCRIPTION TERMINATION

RNA pol II transcription genes may continue up to hundreds or even thousands of nucleotides beyond the end of a coding sequence. Then the cleavage of RNA strand occurs by a complex which appears to associate with the polymerase. Cleavage of RNA is couple with termination process and it occurs at same consensus sequences. The polyadenylation of mature pol ll  m RNA  occurs at the 3′,which  result in a poly(A) tail; this process is followed by cleavage and  termination. Both processes polyadenylation and termination occurs at same consensus sequence, and both these processes are interdependent.