Phosphorylation of CTD of a subunit of 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


Phosphorylation of CTD of a subunit of Pol II
RNA polymerose II is found in a non-phosphorylated form (called IIA) at the time of binding to the promoter. It gets altered into a phosphorylated form (called IIO), before it uncouples from preinitiation complex to take part in the onset and elongation of transcription (Fig. 32.18).

Extensive phosphorylation takes place in the carboxy-terminal domain (CTD) 'tail' of the largest subunit of RNA polymerase II. TFIIH has been shown to be the CTD kinase responsible for phosphorylation of CTD. The kinase is held in check and its activity is increased with the assembly of pre-initiation complex, and with the addition of TFIIE. TFIIH actually consists of five subunits and carries out activities other than phosphorylation of Pol II. In particular, the interaction of TFIIH, TFIIE and TFIIJ may be important for transcription.
 
A model showing the action of transcription factor TFIIH (a kinase) on the carboxy terminal domain (CTD) tail of the largest subunits of RNA . polymerase II (note that the polymerase can elongate the RNA on DNA template,, without the transcription factors, once it binds to promoter and gets phosphorylated).
Fig. 32.18. A model showing the action of transcription factor TFIIH (a kinase) on the carboxy terminal domain (CTD) tail of the largest subunits of RNA . polymerase II (note that the polymerase can elongate the RNA on DNA template,, without the transcription factors, once it binds to promoter and gets phosphorylated).