Domain Structure in Transcription Factors

Question 1

Domains in Transcription Factors

Answer 1

• Dimerization domains
• DNA-binding domains
• Activation Domains

Question 2

same protein

Answer 2

homodimer

Question 3

• similar, but different protein

Answer 3

heterodimer

Question 4

Dimerization domains

Answer 4

• protein-protein interactions -

Question 5

DNA-binding domains

Answer 5

• protein-DNA interactions
• bind to DNA in sequence specific manner.
• Must be a pair of DNA binding domains in the correct conformation by dimerization of protein

Question 6

Activation domains

Answer 6

• protein-protein interactions
• activate transcription or prevent transcription (gene silencing)

Question 7

Leucine Zippers in bZIP Transcription Factors

Answer 7

• protein-protein domain
• Leucine at 1, 8, 15, 22 forms hydrophobic face. Two helices form a dimer based on hydrophobicity
• acts like a zipper to make 2 dimerization domains interact

Question 8

bZIP

Answer 8

• transcription factor
• ZIP - Zipper Dimerization Domain
• b - basic (positively charged) DNA-binding domain.
• basis for interactions of negatively charged DNA

Question 9

Leucine Zippers and DNA

Answer 9

• zipper is dimerization domain
• b-DNA binding domain
• activation domain
• to interact with all other proteins. located in C-terminal region.

Question 10

Helix-Loop-Helix Transcription Factors b/HLH

Answer 10

• variation of leucine zipper.
• dimerization puts DNA binding domain into correct spot to bind alpha helix due to high content of basic AA - weak chemical interactions
• AA in loops act non-specifically with phosphate of DNA backbone (not dependent on sequence of DNA)

Question 11

Specific interactions

Answer 11

• due to ionic and hydrogen bonds between the R groups of the amino acids and information in the major groove of DNA.

Question 12

Zinc fingers

Answer 12

• DNA binding domains
• 2 cysteines (on right) , 2 histidines (on left)
• Both secondary structures represented in zinc finger

Question 13

Tandem Repeats of Zinc Fingers

Answer 13

• rare to have single zinc fingers in a protein
• multiple fingers needed to interact strongly with DNA
• multiple contacts good fit
• identity of AA determine specificity of DNA binding

Question 14

TFIIIA

Answer 14

• TF - transcription factor
• III - RNA pol III
• A - first discovered

Question 15

Video

Answer 15

• uses zinc fingers to place genes and traits
• each additional zinc finger increases specificity.