Question

Can someone please help with b, c, and d? Thank you.

3. Back at the core promoter again: يه إ Totod on sword The six things that bind to the promoter are: TFIIA, B, D, E, F and RNA polymerase. a) What is the order that binding occurs? TEIID, TFITA, TFI1B, TFIF-BNA Plymerase), TFIE b) Where does the first TF bind, and what are its particular subunits that allow binding to occur? The C it's liv c) What is the function of the very last TF that arrives at the core Promoter? d) Once RNA polymerase and all of the TFs are in place, what happens next?

Answer 1

The question is concerned with the process of transcription. During transcription, a protein-initiation complex (PIC) is formed which recruits the protein-complex RNA Polymerase to the site and the transcription starts.

The PIC is formed at various steps. The first step involves the binding of TBP (Tatabox binding protein) to the TATA Box. This binding facilitates the recruitment of TFIID, the first transcription initiation factor which binds to TBP and the promoter. These interactions are stabilized by TFIIA. TFIIB is then recruited which further stabilizes the TATA Box-TBP complex. This facilitates the recruitment of other transcription factors TFIIF and RNA Polymerase. The TFIIF also stabilizes the RNA Polymerase. RNA Polymerase then recruits TFIIE which facilitates promoter melting. It also recruits the last TF i.e. TFIIH. TFIIH is a helicase that promotes the unwinding of the DNA helix.

With this information, we can answer the questions:

a) The correct order of the binding proteins hence is TFIID, TFIIA, TFIIB, TFIIE, RNA Polymerase, TFIIF, TFIIH.

b) The first TF is TFIID. As mentioned it binds to the Promoter region. It has two subunits: TBP which interacts directly with the TATA-Box region and the TAF subunit which binds to the non-TATA Box promoter regions.

c) The last TF that arrives at the promoter is TFIIH. This is a helicase. It hydrolyzes ATP and uses this energy to unwind the DNA, thereby exposing the bases for recognition by the RNA Polymerase.

d) Once all the TFs and the RNA Polymerase are placed properly, transcription initiation comes to an end and transcription elongation begins. TFIIH unwinds few base pairs next to the promoter. RNA Polymerase uses the energy released from the hydrolysis of ATP to move forward along the DNA. It recognizes the base pairs and synthesizes an RNA strand that is complementary to the DNA bases.