Transcriptional Regulation in Eukaryotes - Lecture 12 Flashcards
What happens when you extract DNA that has been digested with DNAase from a tissue not expressing a gene of interest?
Single band
What happens if you extract DNA that has been digested with DNAase from a tissue that has expressed a gene of interest?
Two bands
What is DNAase hypersensitivity?
○ When a gene is switched off: DNAase can’t access DNA due to the proteins protecting it
○ When a gene is switched on: DNAase can access the DNA as the nucleosomes move around
What is the structure of histones?
○ Non-polar globular domain
○ Positively charged arms (N and C terminal variable basic arm)
How can histones be modified?
○ Methylation
○ Acetylation
○ Phosphorylation
What does methylation do?
○ Adds a methyl group to lys and his
○ Responsible for gene activation and repression and DNA replication
What is acetylation do?
○ Adds CH3CO2- group to lysines of core histones
○ Neutralises the histone arms to loosen association with DNA
○ Responsible for nucleosome assembly and gene activation
What does phosphorylation do?
○ Addition of PO4- to lysines of H1
○ Role in replication
○ Responsible for cell division, transcription and chromatin structure
What are the proteins at the enhancer made up of?
○ Transcription activation domain
○ DNA binding domain
How are histones moved?
○ Enzymes involved in histone acetylation
○ Enzymes involved in physically pushing the chromain - ATP dependent
What is the signal transduction pathways which result in phosphorylation of transcription factors?
○ 1st step: Ligand-receptor interaction at plasma membrane
○ 2nd step: Generation of 2nd messenger small molecule
○ 3rd step: Activation of proteins kinases
○ 4th step: Regulation of transcription factor activity
○ 5th step: Modifications to charge, structure, protein-protein interactions
○ 6th step: DNA binding, activation, nuclear localisation, degradation
What is a protein kinase?
Adds a phosphate group to another protein
How is a gene activated in response to a viral infection?
○ Ligand interacts with receptor
○ Receptor is coupled directly with protein kinase and activates it
○ Kinase phosphorylates STAT monomers
○ STAT monomers form a dimer and can enter the nucleus and bind to the enhancer
How is a gene activated when a hormone interacts with a receptor?
○ Receptor is coupled to a protein that converts ATP to cAMP
○ cAMP activates protein kinase A
○ Protein kinase A phosphorylates CREB (transcription factor)
○ CREB recruits CBP
○ CBP is capable of histone acetylation so it can access the chromatin
What are nuclear hormone receptors?
○ Large superfamily of ligand-dependent transcription factors/receptors
○ Can get into the cell without a need for a cell receptor
