Question

Pol II promoters can have up to four functional elements.

Draw a generic Pol II promoter with all four elements and their positions relative to the start of transcription (+1).

What are the Pol II associated transcription factors that help in the assembly of the initiation complex?

What is the sequence of the assembly of the general transcription factors?

Answer 1

RNA polymerase II is an eukaryotic enzyme which can bind to the promoter element of the DNA only with the presence of the transcription factors. These actors helpin the formation of an iitiation complex for the iitiation of the transcription process.

The transcription factors are labelled in a serial order alphabetically right from A to H. Each of these transcription factors get attached to the promoter site and the activators in a particular order to initiate the formation of the transcription initiation complex.

TFIID is the first transcription factor that binds to the TATA box which is the determining site on the where will the transcription begin. This initial complex formed of the TFIID and the TATA box is the site to which the subsequent transcription factors attach themselves to.

Next, TFIIA and TFIIB factors attach themselves to the complex and in turn form another transcription complex. This is followed by the RNA polymerase II and TFIIF.The transcription initiation complex is complete only after the attchment of TFIIE and TFIIH occurs.

TFIIH in turn helps in the unwinding of the double helix structure which helps in the transcription process to start off.