Question

Beginning with the binding of TFIID and extending through the addition of the PolyA tail, please outline the entire process of transcription in eukaryotes. Be sure that you address the transcription factors, binding of RNA Polymerase, the modifications made to the mRNA as transcription is occurring, the CTD tail and the phosphorylation patterns and what significance those have, and alternative splicing.

Answer 1

Answer has been attached image below-

In eukaryotes transcription factors mediate the binding of RNA polymerase at promoter.  

Group of transcription factirsxare present includes TFIIA, TFIIB, TFIIH, TFIIE , TF II F etc.

TFIID is the factir which recognizes promoter sequence.

This TFIID is made up of TBP and TAFs ( TATA binding protein and TATA binding protein associated factors).

TBP is the first protein recognize promoter sequence after binding it cause distortion of DNA which serve as a platform where rest of protein binds and form transcription initiation complex.

Later TFIIA, TFIIB ( binds to initiator sequence), TFIIF ( recruit RNA polymerase, and finally TFIIE and TFIIH.

This complete the formation of pre initiation complex ( PIC).

In this complex TFIIH has helicase as well as kinase like activity. RnA polymerase has alpha C terminal domain tail, which has heptamer sequence repeats approximately52 no . TFIIH when phosphorylate this CTD tail , the RNA polymerase get activated and shed all the factor associated with it and start transcription.

After initial 10 base pair of transcription, RNA polymerase enter in to elongation phase , during elongation phase as RNA come out side all the modifications occur at the same time . All the enzymes required for the modifications present at aloga CTD of RNA polymerase. These modification includes

a) 5' Cap - at 5 end csp is added in form of 7 methyl guanosine which play an important role in translation.

B) splicing- during splicing introns are excised and exons are ligated by splicing.

c) poly A,tail aded at the end of mRNA , provide stability to mRNA

For better understanding formation of Preinition complex has been attached below as image

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