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Transcription Factors Involved in RNA Synthesis

Transcription factors are proteins that assist in the production of RNA. Some are involved in the initiation phase, while others are present during the elongation phase of RNA synthesis.

The RNA molecule is synthesized from a strand of DNA with the help of several proteins. The main protein involved in the synthesis of mRNA is RNA Polymerase II, which is an enzyme that builds the pieces of nucleotides according to the code present in the DNA strand. In order for RNA Polymerase II to do this, it requires several other proteins to assist in the process. These proteins are known as transcription factors.

Phases of Transcription

There are four phases in which mRNA synthesis takes place. The assembly phase consists of the gathering of RNA polymerase II at the starting point on the DNA strand, along with binding proteins that stabilize the transcription complex, including TBP. The initiation phase starts the synthesis of RNA, and the elongation phase lengthens the RNA strand. During the termination phase of transcription, the RNA strand is completed and released.

Transcription Factors Required During Initiation

There are several transcription factors involved in the initiation of mRNA synthesis. Each one has a specific function.

TFIIA – This protein affects the transcription factor binding site of TFIIB and TBP at the starting point for RNA synthesis.

TFIIB – This protein binds to TBP and signals the approach of the RNA Polymerase II – THIIF complex. Both of these complexes come together.

TFIIE – Signals TFIIH to approach the transcription complex. It also has catalytic properties including ATPase and helicase activity.

TFIIF – Binds to RNA Polymerase II and subsequently to TFIIB. It prevents RNA Polymerase II from binding to the wrong DNA sequences.

TFIIH – This proteins unwinds the DNA sequence at the starting point for RNA synthesis. It also activates RNA Polymerase II by phosphorylating it. TFIIH is also required to attract repair proteins.

Transcription Factors Required During Elongation

There is another set of proteins involved during the elongation phase. They have a similar function, which is to phosphorylate RNA Polymerase II.

  • ELL
  • p-TEFb
  • SII (TFIIS)
  • Elongin (SIII)

Reference:

Nelson, David L. Lehninger Principles of Biochemistry 4th ed. W.H. Freeman and Company. 2005

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