Question

Regulation of mRNA transcription in eukaryotes is tightly regulated. Describe the elements (regions of the DNA) involved and what their function is. Describe the transcription factors (proteins) involved in initiating transcription.

Answer 1

Transcription in eukaryotes involves the following regions of the DNA:

- TATA box- The TATA box has the sequence 5'-TATAXAX where X is A or T. It is present at the -30 upstream region of the DNA.

- Initiator or inr sequence- It is present at the +1 nucleotide position on the DNA and is rich in pyrimidines. The TATA box and Inr sequence are responsires for deciding the position at which transcription starts.

- CAAT box and GC box- these are regulatory sequences which determine the drequencf of initiation of transcription. They can function in either orientation.

The transcription factors involved in initiating transcription in eukaryotes are:

TFIID- It recognises the TATA box and the Inr sequence

TFIIA- It stabilises the binding between TATA binding protein (TBP) and TBP associated factors

TFIIB- It helps in deciding the start point for transcription

TFIIF- It is responsible for the recruitment of RNA polymerase II

TFIIE- It helps in the recruitment of TFIIH

TFIIH- It shows helicase activity and helps in the transition from the closed promoter complex to the open promoter complex.