Transcription Factors Flashcards
What is the definition of a transcription factor?
Transcription factors are adapter molecules that detect regulatory sequences in the DNA and target the assembly of protein complexes that control gene expression
What are enhancers?
DNA elements that activate gene expression from a distance, irrespective of their orientation
What are silencer elements?
DNA elements that repress gene expression from a distance, irrespective of their orientation.
Properties of enhancers
DNaseI hypersensitive regions
P300 binding sites
Monomethylation of H3 lysine 4
Acetylation of H3 lysine 27
What do pioneer transcription factors do?
Independent nucleosome / chromatin binding
Precedes other factors binding
What are the passive roles of pioneer factors?
Binding speeds inductive responses
Partially bound - inactive enhancer
Induction
Fully bound - active enhancer
What are the active roles of pioneer factors?
Opening chromatin
Enables other factors to be bound
Type I receptor binding
Steroid receptors
Bind as homodimers
Bind in cytoplasm to HSP90
Hormone binds and completes folding of receptor
Disassociates from HSP90 and then binds to target gene in nucleus
Type II receptor binding
Unliganded receptors in nucleus
Present in nucleus
May sit on target genes to repress them
Hormone binds to receptor and causes activation
What are the two common binding domains?
Ligand binding domain
DNA binding domain
What does an agonist do?
Activate the receptor
What does an antagonist do?
Prevent activation of the receptor
What does a partial agonist do?
Activate but to a lower level than agonist (can act like partial antagonists since they can compete with full agonists)
What does an inverse agonist do?
Lead to inverse activity of the receptor
What common factor do ligands have?
Largely non-polar character
