Control of Immediate Early Gene Transcription Flashcards
What is the activation of a signalling pathway?
Transient
What are the effects of signalling pathway activation?
Transient or long term
What is the usual half life of most proteins?
Less than 24 hours
How can the output be varied by activating a signalling pathway?
Amplitude
Duration
Sub cellular location
Context
What are PC12 cells?
Cell line derived from rad adrenal medulla
What do PC12 cells response to?
NGF and EGF
What do NGF and EGF activate?
The classical ERK1/2 MAPK cascade
How do NGF and EGF act differently in PC12 cells?
NGF activates ERK1/2 for longer
EGFR is internalised faster
NGF promotes stronger nuclear activation of ERK1/2
NGF activates Rac1 at the membrane, EGF does not do this well
NGF causes neuronal differentiation, EGF induces proliferation
What causes the difference in NGF induced neuronal differentiation and EGF induced proliferation?
The different in ERK activation
How does NGF increase ERK1/2 nucleur activation?
ERK1/2 has to translocate from the cytoplasm to the nucleus and therefore the longer the activation, the more ERK can translocate
What is gene transcription controlled by?
Transcription factor recruitment / activation of gene promoter
Chromatin environment
How does transcription factor recruitment / activation of gene promoters effect gene transcription?
Promoters can be regulated by multiple transcription factors
Multiple pathways converge on one transcription factor
How does chromatin environment effect gene transcription?
Chromatin structure can be stably modified during cell development or after cell stimulation
- e.g. methylation allows you to have open and closed areas for chromatin (closed inhibits transcription)
This changes promoter exposure
How are immediate early genes induced?
quickly after stimulation
What do immediate early genes not need which secondary response genes do?
Synthesis of new proteins e.g. transcription factors
What is IL-10 and why?
An immediate early gene
It is transcribed quickly after activation and cyclohexamide does not effect its transcription
What cyclohexamide do?
Inhibits the production of new proteins
What is IL-6 and why?
A secondary response gene
It is produced slower than IL-10 and is inhibited by cyclohexamide addition
Give example of transcription factors which are immediate early genes
c-fos
c-jun
nur77
Give an example of an immediate early gene which modifies the cytoskeleton
Arc
Give examples of enzymes which are immediate early genes
iNOS
PTGS2/ cox2
Give examples of cytokines/ growth factors which are immediate early genes
IL-10
IL-1
HB-EGF
How does phosphorylation control transcription factors?
It promotes cytoplasmic location in some cases
Can also promote nucleur location
Give an example of how phosphorylation induces cytoplasmic location
Akt induces FOXO phosphorylation which causes 14-3-3 binding and cytoplasmic location
Inhibition of Akt induces FOXO movement into the nucleus for transcription
Give an example of how phosphorylation causes nuclear location
JAK causes phosphorylation of 2 STAT molecules
The STAT molecules dimerise and move into the nucleus
Describe CREBs function
Promotes immediate early gene transcription which causes:
- development
- regulation of metabolism
- synaptic function
- Innate immune function
What is CREB?
A transcription factor
What family is CREB a member of?
bZIP