Regulated Transcription- Lecture 24

Question 1

What are the three domains of transcription factors and what do they do?

Answer 1

DNA binding domain (recognizes a specific DNA sequence)
dimerization domain (joins two monomers into a complex to increase total number of unique transcription factor proteins)
activation domain (interacts with other proteins to enhance the transcription initiation rate

Question 2

What binding motifs can transcription factors express?

Answer 2

classic heliz-turn-helix (three alpha helice cylinders)
zinc finger motif (one alpha helix and one beta sheet
leucine zipper motif (two alpha helices, each contributed to by a separate protein molecule)
two transcription factor molecules (each contribute a binding helix)

Question 3

What can pionering transcription factors recruit to change the state of local chromatin?

Answer 3

histone-modifying enzymes

chromatin remodeling complex

Question 4

What is DNA methylation and what is it’s purpose?

Answer 4

methylation of C residues in CpG dinucleotides (normally located at/near promoter regions)
serves as a recognition site for binding of proteins that, in turn, recruit enzymes that alter the properties of local chromatin- methylation disrupts the binding, resulting in decreased transcription

Question 5

What is the pattern of global methylation throughout development?

Answer 5

Pre-implantation: all methylation marks erased in gamets save for 1 allele of imprinting center
Implantation: entire genome methylated except CpG islands
Post-implantation: genes that were needed for early development only are now methylated and tissue specific genes undergo demethylation