Transcriptional regulation in eukaryotes - Lecture 11 Flashcards
What is the structure of histones?
A globular protein
Has arms that contain amino acids with a net positive charge
Highly conserved in eukaryotes
High proportion of basic amino acids
What are the three methods of post translational modification of histones?
Methylation
Acetylation
Phosphorylation
What is methylation?
-CH3 groups are added to amino acids lys and his
Involved with gene activation and repression, DNA replication
Dialling down
What is acetylation?
Addition of CH3COO2- group to lysines of core histones
Involved in nucleosome assembly and gene activation
Dialling up
What is phosphorylation?
Addition of PO4 to lysines of H1
Involved in cell division, transcription, chromatin structure
What is the class II regulatory region?
Enhancers have multiple binding sites for sequence specific transcription factors
Co-operate and interact with polymerase
Position and orientation independent, meaning they can be put anywhere in the gene
What is the meaning of the class II regulatory region structure?
Has a bipartite structure
This means it has two domains
Transcription activation domain, DNA binding domain
How does transcriptional stimulation in eukaryotes work?
The promotor and enhancer have different components which means they can interact and bind
There is recruitment of general basal factors/polymerase and HATs and chromatin modifier complexes (They recruit polymerase and modify chromatin)
What is the signal transduction pathway?
- There is ligand-receptor interaction at the plasma membrane
- This generates the second messenger (like cAMP)
- Second messenger activates protein kinases
- Protein kinases regulate transcription factor activity
- There are charge, structure and protein- protein interactions
- This causes DNA binding, activation, nuclear localisation and degradation
What is the overall process of the activation of transcription by signal transduction?
1.Gene activation in response to viral infection
2. CREB - gene activation by cyclic AMP
What is the process of gene activation in response to viral infection?
Ligand binds to the receptor
This causes the activation of transcription factor
The transcription factor binds to enhancer and activates transcription
What is the process of CREB?
The hormone receptor interaction increases cAMP
This activates protein kinase A
Protein kinase A enters the nucleus and generates CREB
What are nuclear hormone receptors?
A large superfamily of ligand dependent transcription factors
What is the relevance of nuclear hormone receptors being hydrophobic?
It means they don’t bind to receptors which means they instead enter the cell
What is an outline of the process of hydrophobic steroid hormones entering the cell?
The hydrophobic steroid hormone diffuses through the plasma membrane
It binds to a receptor
The receptor translocates to the nucleus and activates transcription
