BBOL-Regulation of gene expression Flashcards
1
Q
What is spatial control?
A
Involves location of cell and the environment that surrounds it
2
Q
What is temporal control?
A
When genes require expression, e.g. staged of foetal developmental
3
Q
How is protein production controlled?
A
- Control can be exerted at every step from DNA to protein
- Genes can be regulating transcription itself or by post-transcriptional regulation
- Transcriptional control, RNA processing control, RNA transport and localisation control, mRNA degradation control and protein activity control
4
Q
Describe transcriptional control
A
- Regulation of transcription is the most common form of control for protein production
- Binding of RNA polymerase: promoters and transcription factors
- Long range control- locus control regions
- Chromatin remodelling- histones and histone deacetylases
- DNA methylation- CpG islands and imprinting
5
Q
What proteins control gene expression?
A
- Transcription factos bind to DNA in the major groove of the double helix
6
Q
What are DNA binding motifs?
A
- Gene regulatory proteins contain these and they are part of the protein that binds to DNA
7
Q
How do gene switches work?
negative regulation
A
- Bound repressor protein prevents transcription
- Ligand binds to remove reg. protein from DNA
- Addition of ligand switches gene on by removing repressor protein
- Ligand binds to allow regulatory protein to bind to DNA
- Removal of ligand switches gene on by removing repressor protein
8
Q
How do gene switches work?
positive regulation
A
- Bound activator protein promotes transcription
- Ligand binds to remove regulatory protein from DNA
- Addition of ligand switches gene off by removing activator
- Removal of ligand switches gene off by removing activator protein
9
Q
What do repressors do?
A
- Turn genes off
- Prokaryotes co-ordinately regulate related genes by clustering them: operon
- Genes can be regulated by environmental signals, e.g. tryptophan repressor
- Tryptophan repressor binds to the operon promoter and turns transcription off
10
Q
What do activators do?
A
- Bind to promoter and interact with RNA polymerase to initiate transcription
- In bacteria, binding of activator to DNA controlled by interaction of a metabolite or other small molecule
11
Q
How are prokaryotic genes controlled by multiple signals?
A
- Lac operon controlled by 2 signals- activator and repressor
- Controls synthesis of B-galactosidase that breaks down lactose to glucose in growth medium control activity of repressor and activator
12
Q
How are eukaryotic genes controlled?
A
- General transcription factos needed for all genes
- Gene specific regulation provided by different combinations of regulatory proteins
- Regulatory binding sites may be upstream (5’) , in introns or downstream (3’) of gene (DNA looping facilitates interaction)
- Multiple regulatory transcription factors regulate any one gene
13
Q
How does regulation occur over long distances?
A
- Some control elements are many 100s of base pairs from the gene
- Can control activation of several nearby genes through chromatin remodelling- Locus Control Region (LCR)
14
Q
How is transcription factor (TF) activation regulated?
A
- Activity of regulatory TF may be controlled by protein synthesis, covalent mod, ligand or inhibitor binding that sequester the protein or affect DNA binding ability
- E.g. hormone receptor binding in response to ligand binding
- Ligand binding to GPCRs can lead to gene activation through intracellular signalling pathway- TF activation
- Binding of inflammatory cytokine TNFa leads to degradation of inhibitor protein and activation of NFkB
15
Q
Describe epigenetics
A
- Changes made to DNA that do not involve changes to the sequence
- Control of ‘packaging’
- Chromatin regulation (for DNA to loop and allow regulatory protein interaction accessible and chromatin can remodel in response to activator binding and acetylation pattern of histones can allow recognition and binding by activators)
