transcriptional regulation Flashcards
(19 cards)
What proteins increase gene expression by aiding the binding of RNA polymerase?
Proteins that enhance transcription initiation
These proteins improve the efficiency of RNA polymerase binding.
What is the function of proteins that inhibit RNA polymerase?
They decrease gene expression
These proteins block the transcription process.
What are the genes involved in the lac operon that encode proteins for lactose uptake and utilization?
- lacZ (β-galactosidase)
- lacY (β-galactoside permease)
- lacA (galactoside acetyltransferase)
These genes are only expressed when lactose is available.
What does lacI encode in the lac operon?
Lac repressor
This protein is expressed constitutively.
What happens when glucose levels are low in bacterial cells regarding cAMP?
High concentrations of cAMP bind CAP protein, increasing transcription of the lac operon
CAP binds to operator DNA sequences.
What blocks transcription when lactose levels are low?
LacI protein binds to lacO DNA sequences
This prevents RNA polymerase from initiating transcription.
What is the role of the T7 promoter in engineered plasmids?
It drives expression of an inserted gene of interest
The T7 promoter is derived from bacteriophage T7.
What is the purpose of IPTG in bacterial cultures transformed with expression plasmids?
IPTG binds to LacI, allowing T7 RNA polymerase to transcribe the gene sequence
IPTG is similar in structure to allolactose.
What are the types of gene expression in complex eukaryotes?
- Constitutive expression
- Temporal expression
- Spatial expression
- Responsive expression
These types describe when and where genes are expressed.
What is a characteristic of eukaryotic promoters?
Not all core sequence elements are present in every gene promoter
Most house-keeping genes have TATA boxes, but not all.
What is the structure of the TBP-DNA complex?
Symmetrical saddle structure with topologically identical halves
Contains protein-protein and protein-DNA contacts.
What is the function of TFIIH in RNA Pol II transcription initiation?
Catalyzes unwinding of DNA and phosphorylates the polymerase RPB1 CTD
TFIIH recruits other factors for transcription.
What stabilizes the binding of RNA polymerase during pre-initiation complex assembly?
Activators and the mediator complex
The mediator complex associates with the CTD tail of the polymerase.
What is the structure of transcription activators?
Modular structure with separate activation and DNA-binding domains
This allows for flexible interactions with DNA.
How do transcription regulatory proteins typically bind to DNA?
As dimers
This increases the range of binding specificities.
What are the types of activating regions in transcription factors?
- Acidic
- Glutamine-rich
- Proline-rich
These regions lack a defined structure and interact with other proteins.
What is an example of repression in gene expression?
Lac repressor blocking lacZ gene promoter
This demonstrates how repression can affect transcription.
What role do factors IX and VIII play in the coagulation system?
Pivotal role; lack results in bleeding conditions (haemophilia A and B)
Factor IX is expressed in the liver.
What caused a boy from Bangkok with haemophilia B to become asymptomatic at puberty?
Mutation in a binding site for a liver-specific transcription factor led to reduced factor IX expression
Testosterone binding to the androgen receptor increased transcription.
