Transcription factors in eukaryotes

(See figure in previous post)
Without transcription factors, RNA polymerase will not properly transcribe in vivo. In the book, there are two theories about how TF's work.

1) Transcription factors attach to the TATA box (a promoter sequence). There are many different kinds of TF's (see table 3.1). RNA polymerase then attaches to the same place.

2) TF's and RNA polymerase are already assembled, and the complex attaches to the promoter.

In both cases, the RNA is closed until a ATP-dependent process occurs and make it open. The TF's dissociate after transcription starts.

To note:
CTD: Carboxyl-terminal domain. It is a region in one end of the RNA polymerase which interacts with a protein complex called SRB/MED. SRB/MED aids in transcription