Control of Gene Expression 1 Flashcards
(24 cards)
Why isn’t the entire genome expressed in every cell?
Wasteful of energy and resouces
What are some of the diseases that can arise due problems in regulation?
Cancer
Developmental diseases (early protein synthesis)
Chronic diseases (abnormal gene expression)
At what stages can regulation of eukaryotic gene expression occur?
Transcription
RNA processing
mRNA transport
mRNA translation
mRNA degradation
Protein degradation
What are trans-acting regulatory molecules and what do they do?
Proteins which are synthesised from other genes
DNA-binding domain and transcription activation domain
Bind to regulatory sequence on DNA to affect transcription/initiation
What are cis-acting regulatory sequences?
Short sequences of DNA which influence transcription initiation on the same DNA molecule
Found in non-coding regions
Interacts with DNA-binding proteins to affect initiation
What is the TATA box?
Highly conserved promoter in eukaryotic DNA
Helps RNA polymerase II to bind
Where is the TATA box found?
-34 to -26 upstream of start codon
What are promoters?
Site where transcription initiation complex is assembled
What are transcription factors?
Proteins which ensure genes are correctly expressed at a specific time and in response to internal or external stimuli
What are the two main groups of transcription factors?
General transcription factors
Sequence-specific DNA-binding transcription factors
What is the function of general transcription factors?
Bind at promoters and are required to form a pre-initiation complex to recruit RNA polymerase II
What are the functions of sequence-specific DNA-binding transcription factors?
Facilitate or prevent transcription initiation of specific promoters
Allow general transcription factors to bind to promoter
What do all RNA polymerase II-transcribed genes require?
General transcription factors
What is the ‘core’ promoter?
Where RNA polymerase II and GTFs bind
What is an example of a ‘core’ promoter?
TATA box
What is a ‘proximal’ promoter?
Where other transcription factors bind which affect transcription initiation
Found upstream of ‘core’ promoter
What is the transcription initiation complex?
Several general transcription factors come together at the ‘core’ promoter in a specific order to help RNA polymerase II bind
What regulates the activity of the transcription initiation complex?
Sequence-specific DNA-binding transcription factors
How does a mutation in the coding sequence of a transcription factor affect biological processes?
Mutant transcription factor
Binds DNA differently resulting in abnormal mRNA expression of target genes
Abnormal protein expression results in altered regulation of pathways
How does a mutation in the transcription factor binding sequence affect biological processes?
Altered binding of transcription factor to target gene
Abnormal mRNA expression of target gene resulting in abnormal protein expression
Altered regulation of pathways
In what ways can hormones affect gene expression?
Bind to receptors on cell membrane and trigger a signalling cascade
Enter cells and bind to intracellular receptors; interact directly with DNA
Describe an example where polyadenylation is used to regulate gene expression.
U1A protein can bind its own pre-mRNA when in high concentrations just upstream of polyA site/signal to inhibit polyadenylation
Incomplete processing so not translated
When U1A levels are low, pre-mRNA is polyadenylated and more U1A is able to be formed
What is U1A?
Protein involved in spliceosome
Describe an example of alternative splicing.
Fibronectin in liver cells and fibroblasts is coded for by the same gene but their mRNAs contain different exons
Liver secretes soluble fibronectin into blood and contains a domain to aid clot formation
Fibroblasts secrete fibronectin which contains EIIIB and EIIIA binding domains to make it more adhesive
