Formation of preinitiation complex with RNA polymerase II (Pol II)

Content
Expression of Gene : Protein Synthesis 2.  Transcription in Prokaryotes and Eukaryotes
Transcription in prokaryotes 
Single RNA polymerase in E. coli
Promoter sites for initiation of transcription in prokaryotes
Initiation and elongation of RNA synthesis in prokaryotes
'Inchworm model' for elongation of transcript
Elongation arrest vs termination of transcription
Termination and antitermination of mRNA synthesis in prokaryotes
Transcription in eukaryotes 
Multiple RNA polymerases in eukaryotes
Promoter, enhancer and silencer sites for initiation of transcription in eukaryotes
Transcription factors and initiation of RNA synthesis in eukaryotes
Formation of preinitiation (transcription) complex with RNA polymerase II (Pol II)
Structure and role of TFIID and other transcription factors (TBP, TAFs)
TFIIB domains for interaction with TFIID/TATA complex
Phosphorylation of CTD of a subunit of Pol II
Formation of pre-initiation complex with Pol I and Pol III
Separate DNA binding and transcription activation domains
Transcription factors and elongation of RNA chains in eukaryotes
Chromatin structure and transcription
Transcription in mitochondria
Transcription of vertebrate mtDNA
Transcription of yeast and plant mtDNA
Transcription in chloroplasts
Formation of preinitiation (transcription) complex with RNA polymerase II (Pol II)
The promoter sequence responsible for constitutive expression of common genes (also called house keeping genes) in all cells is called generic promoter, which can not bring about regulated expression (tissue or stimulus specific). Initiation of transcription on this generic promoter by RNA polymerase II requires the action of several transcription factors (variously designated in humans, rat and yeast; Table 32.3) in the following defined order (Fig. 32.16) : (i) TFIID binds at the TATA box, which permits (ii) the association of TFIIA and TFIIB; (iii) only after binding of TFHB, forming the so called DB complex, RNA polymerase associates to promoter site; (iv) RNA polymerase is escorted to the promoter by TFIIF to form a transcription complex; (v) orderly addition of TFIIE, TFIIH and TFIIJ helps in the initiation. The requirement of TFIIA and TFIIE has not been found universal. The function of TFIIA can be performed by TFIIG or TFII I (two factors discovered in 1990's); TFIIE, on the other hand, though needed for adenovirus (Ad) ML, H2B and H4 prmoters, has not been found essential for immunoglobulin heavy chain gene (Ig H) promoter. Besides the above transcription factors, hundreds of other transcription factors have been discovered, which are needed for tissue or stimulus specific transcription.

(a) Formation of transcription complex at the promoter for RNA polymerase II. (b) Association of TBP with different groups of TAFs to form transcription factors used in the formation of transcription complexes.
Fig. 32.16. (a) Formation of transcription complex at the promoter for RNA polymerase II. (b) Association of TBP with different groups of TAFs to form transcription factors used in the formation of transcription complexes.

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