Transcription Is Initiated by RNA Polymerase without the Need for a Primer known as de novo synthesis 

TLS Online TPP Program

#Id: 6493

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6494

#Unit 3. Fundamental Processes

Model of Formation of the DABPolF Complex

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#Id: 6495

#Unit 3. Fundamental Processes

TFIIB, TFIIE, and TFIIH are required to melt DNA to allow polymerase movement. The last factors to join the initiation complex are TFIIE and TFIIH. 

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#Id: 6496

#Unit 3. Fundamental Processes

TFIIH is the only general transcription factor that has multiple independent enzymatic activities. Its several activities include an ATPase, helicases of both polarities, and a kinase activity that can phosphorylate the CTD tail of RNA polymerase II (on serine 5 of the heptapeptide repeat). TFIIH is an exceptional factor that may also play a role in elongation.

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#Id: 6497

#Unit 3. Fundamental Processes

On a linear template, ATP hydrolysis, TFIIE, and the helicase activity of TFIIH (provided by the XPB and XPD subunits) are required for polymerase movement. This requirement is bypassed with a supercoiled template. This suggests that TFIIE and TFIIH are required to melt DNA to allow polymerase movement to begin. To extend elongation into the transcription unit, a kinase complex called P-TEFb is required. P-TEFb contains the CDK9

kinase, which is a member of the kinase family that controls the cell cycle. P-TEFb acts on the CTD to phosphorylate it further on serine 2 of the heptapeptide repeat.

TLS Online TPP Program

#Id: 6498

#Unit 3. Fundamental Processes