Control of Gene Expression Flashcards
What does the structure and function of a cell depend on?
What proteins are produced and in what quantities
What do differences in gene expression depend on?
In both transcription and translation
Give an example relating to gene A, gene B and gene C of the dependence in gene expression on transcription and translation.
Gene A might not be transcribe whilst gene B is but gene B is not translated as much as gene C
Why does the control of gene expression matter?
- All cells within complex multicellular organism contain the same DNA
- But cells are made up of many different types of cells and tissues
- The difference is caused by which genes are expressed in the genome at which time
When can gene expression be controlled?
At different points in the pathway from DNA to protein
What is the first point of controlling gene expression?
Between DNA and RNA transcript = transcriptional control
What is the second point of controlling gene expression?
Between RNA transcript and mRNA = RNA processing control
What is the third point of controlling gene expression?
Between mRNA in the nucleus to mRNA in the cystosol = RNA transcript and localised control
What is the fourth point of controlling gene expression?
From mRNA to protein = translation control
What is the fifth point of controlling gene expression?
Between mRNA to an inactive mRNA = mRNA degradation control
What is the sixth point of controlling gene expression?
Between protein becoming an inactive protein or an active protein = protein activity controlling
How many RNA polymerase are there that trascribe different sets of genes?
3
What does RNA polymerase I transcribe?
5.8S, 18S, 28S rRNA genes
What does RNA polymerase II transcribe?
All protein-coding genes, including snoRNA genes, mi RNA genes, siRNA genes, IncRNA genes and most snRNA genes
What does RNA polymerase III transcribe?
tRNA, 5s rRNA, some snRNA and genes for smaller RNAs
What does the “S” value which RNA are assigned to?
The rate of sedimentation in an ultiracentrifuge
If the RNA is assigned a large “S” value what does that show about the RNA?
That it is large
What are the general principles of initiation of transcription?
- Promoter is required for RNA polymerase to bind
- RNA polymerase interacts with general transcription factors when bound to promoter
- Additional control sequences determine when a gene is transcribed
What is a cis-acting regulatory region?
DNA sequences recognised by proteins
What do all regions transcribed by RNA polymerase II (class II) contain?
- Enhancers
- Promoter
What is an enhancer?
Regulatory sites that can be distant from the promoter which acts as the binding site for activator proteins
What is a promoter?
Very close to protein coding region and included initiation site (where a transcription begins and a “TATA” box)
What do trans-acting proteins (transcription factors) do?
Bind to the promoter and enhancer to control transcription from the gene
What do activators and repressors bind to?
The enhancer
What does general transcription factors and RNA polymerase II bind to?
The promoter
What binds to the promoter?
General transcription factors and RNA polymerase II
What binds to the enhancers?
Activators and repressors
Describe the process of the help of basal transcription factors on eukaryotic RNA polymerase II binding to the promotor:
- TATA-box binding protein (TBP) subunit of TFIID binds to the TATA box
- TBP/TFIID complex recruits TFIIB to the promoter
- RNA polymerase II and transcription factors are recruited to promoter
- TFIIH promotes the opening of DNA and phosphorylation of RNA polymerase II
What helps eukaryotic RNA polymerase II bind to promoters?
General transcription factors
What is another term for general transcription factors?
Basal transcription factors
What stage is “TBP/TFIID complex recruits TFIIB to the promoter” in the help of basal transcriptions factors process?
Second
What stage is “TATA-box binding protein (TBP) subunit of TFIID binds to the TATA box” in the help of basal transcriptions factors process?
First
What stage is “TFIIH promotes the opening of DNA and phosphorylation of RNA polymerase II” in the help of basal transcriptions factors process?
Fourth
What stage is “RNA polymerase II and transcription factors are recruited to promoter” in the help of basal transcriptions factors process?
Third
What do activator proteins which are bound to enhancers interact with?
General transcription factors and RNA polymerase II
What is an example of an activator protein?
Gal 4
What does Gal 4 activate when bound to enhancer?
Activates multiple galactose-inducible genes in yeast
Are cis-regulatory regions similar in different genes?
No highly variable
Are promotors similar in different genes?
Generally similar
Are coding regions similar in different genes?
No, specific for the protein encoded by each gene
What does complex regulatory regions enable an organism to do?
Fine-tune gene expression
What doe chromatin structure play a role in?
Eukaryotic gene regulation
What is DNA packed into?
Condensed chromatin
What does the chromatin structure provide on a runaway basal transcription?
A “brake”
What are the 3 mechanism that make DNA more accessible to transcription factors?
- Chromatin remodelling and remodelled nucleosome
- Histone chaperon
- Modification of histones
What happens in making DNA more accessible in the mechanism chromatin remodelling and remodelled nucleosome?
Nucleosomes sliding allowed acmes of transcription machinery to DNA
What happens in making DNA more accessible in the mechanism of histone chaperon?
A. remove histone protein/nucleosome meaning transcription machinery can assemble onto nucleus-free DNA
B. Exchange histone proteins for histone protein variants allowing greater access to nucleosomal DNA
What happens in making DNA more accessible in the mechanism of modification of histones?
Destabilises a compact form of chromatin and attract components of transcription machinery
What can core histones be covalently modified on?
On their N-Terminal
What does histones being covalently modified on N-terminal do?
Alters transcription pattern in areas of histones
What are the 4 different types of histone modification?
- Methylation
- Phosphorylation
- Acetylation
- Ubiquitylation
Where can you find acetyl group found?
On Lysines (K)
Where can you find phosphate groups found?
Serines (S) and Threonines (T)
Where can you find methyl groups found?
Lysines (K) and Argentines (R)
How many ubiquitin amino acid sequences are there?
76
What does histone H3 K9 methylation do to the gene expression?
Represses
What does histone H3 K9 acetylation d do to the gene expression?
Activates
What can be covalently modified directly (excluding histones)?
DNA
What does mentholated DNA do to the gene expression?
Represses
What base pair may be under direct covalently modification?
In the sequence CG
Can cytosine methylation patterns be inherited after DNA replication?
Yes
What is epigenetic?
Change in phenotype that caused by change within the gene sequence
