Question

Last week we discussed the role of general transcription factors in forming the transcription initiation complex in eukaryotes. Next week we will look more closely at the regulation of gene expression and the role played by specific transcription factors. Prokaryotes and eukaryotes utilize very different mechanisms for determining which genes are turned on and off and when. In lieu of the prokaryotic operon model, eukaryotes employ a combinatorics approach utilizing both general and specific transcription factors. For this week’s forum, read the article Transcription Factors and Transcriptional Control in Eukaryotic Cells and answer the following questions.

http://www.nature.com/scitable/topicpage/transcription-factors-and-transcriptional-control-in-eukaryotic-1046

1. What is a transcription factor?

2. Why would a transcription factor have multiple functional domains?

3. What is combinatorics and what role does it play in gene regulation?

4. How have transcription factors allowed more complex organisms to do more with less?

Answer 1

1. A protein binds to DNA and started to regulate expression of transcription or inhibit the mRNA synthesis.

2. In eukaryotes it has lot of TF like TFIIF, TFIIE, TFIIH, TFIIB, TFIIA and TFIID each has specfic role to intiate the transcription. TFIIH role helicase activity it will separate 2 DNA strands. TFIIE maintains the open complex
TFIIF brings the polymerase to TATA box. TFIIA gives stability for polymerase and other TF.TFIIF, H and E
involved in elongation of Transcription. Other factors are for only initiation.

3. Different types of proteins or TF combine together for control gene expression that either turn on or turn off the genes. Eg. Enhancer will activate the gene product present in some where apart from this gene. The cis-regulation
pattern observed in combinatorial regulation.

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